The Danish Late Quaternary marine molluscs

The record of shell-bearing Danish Late Quaternary marine molluscs has been established on the basis of finds made during the systematic geological mapping since 1888, as presented in the publications from the Geological Survey of Denmark, mainly in the I. Række covering the descriptions for the map sheets. Furthermore, special papers on Holocene and Late Pleistocene marine molluscs have been included. Most of them have been listed in one of the preceding chapters on works on Danish sites with marine sediments.


The Danish Late Quaternary marine molluscs
The record of shell-bearing Danish Late Quaternary marine molluscs has been established on the basis of finds made during the systematic geological mapping since 1888, as presented in the publications from the Geological Survey of Denmark, mainly in the I. Raekke covering the descriptions for the map sheets. Furthermore, special papers on Holocene and Late Pleistocene marine molluscs have been included. Most of them have been listed in one of the preceding chapters on works on Danish sites with marine sediments.
1. The Baelt Sea area 2. The Baltic Sea area 3. The Kattegat area with fjords 4. The Limfjord area 5. The North Sea coastal area 6. The Vendsyssel area 7. The Skagen area The regions are figured on the map (Fig. 2) and follow the outline of the geological map sheets except the Skagen area. It should be especially noted that the southern limit during the Holocene of the North Sea coastal region is at Blåvands Huk. Although this area from Varde to the German border has been mapped, no descriptions have been published. However, studies of the Eemian from this region have been published and will be commented upon when presenting the Eemian records from the above-mentioned areas.
The Baelt Sea area has been taken as the region between the Kattegat region and the Baltic, here following Ekman (1953) saying that the boundary between the Baelt Sea and the Baltic proper is the threshold between Gedser and Darss and the southern end of the Øresund, see Fig. 1.
The reason for including the Øresund north of Saltholm (northern and middle Øresund sensu Jensen & Knudsen 1995) in the Kattegat region is that regarding the water from the Baltic the Øresund is a sounda passage -for the brackish water flowing north, but regarding the salt-water from the Kattegat, the Øresund is a fjord down to the threshold between Amager and Limhamn, to quote Thorson (1944a, p. 42).
Only the synonyms mentioned in texts on Danish molluscan finds are included. A list of these synonyms is found heading the Index of species.
The investigations carried out by scientists in the northern Atlantic have given a good base for the evaluation of the Danish Late Quaternary molluscan fauna. These studies have been published mainly in papers on the Zoology of East Greenland, The Godthaab Expedition 1928, the Zoology of Iceland, and the Zoology of the Faroes. However, the Zoology of Greenland has been supplemented by contributions from Macpherson (1971), Lubinsky (1980), the 6. og 7. Thule Expedition til Sydøstgrønland 1931-33 under the leadership of Knud Rasmussen and the Treaarsexpeditionen til Christian den X's Land 1931-34 under the leadership of Lauge Koch.
In the two last-mentioned contributions, especially the animal ecology and the Arctic communities have been treated, which form a very important part in the discussion of the Danish Late Quaternary molluscan assemblages. The following publications on molluscs can be mentioned: northern European seas as given by Feyling-Hanssen (1955, fig. 5) and Símonarson et al. (1998), as seen on Figs 4 and 5 respectively.
The molluscan genera and species are presented in groups within Class, Subclass and Order mainly following the presentation of recent marine molluscs of Danish waters as given by Jensen & Knudsen (1995). When there is no subfossil record at hand the information is taken from the recent data as given by Poppe & Goto (1991, 1993, Jensen & Knudsen (1995) and others as listed previously. To facilitate the use of the index of all molluscan species, a list of synonyms is given as mentioned earlier including the species mentioned in Danish mollusc literature.

Class Polyplacophora Order Neoloricata
Among the seven species recorded in the recent Danish fauna only one, Tonicella marmorea, has been found subfossil in the Vendsyssel area from the Younger Weichselian deposits. It is a circumBoreal species which in Europe is known from northern Scandinavia south to Denmark and recorded from around Iceland (Knudsen 1949a, b) down to Ireland (Poppe & Goto 1991). It is common in Danish waters, being known from the central part of the Kattegat and the Øresund region (Muus 1959), e.g. Subarctic-Boreal-Lusitanian species.
Habitat. Common in shallow water of less than 20 m, otherwise recorded from 0-183 m (Muus 1959).
The lack of information on subfossil finds may reflect difficulty in determination when the species is found in the subfossil state of preservation with the shell parts apart. Polyplacophora do occur as seen from the Skagen Well where finds have been recognised at the 70.10-70.30 m and the 37.0-37.25 m levels, viz. during the Subboreal and the Subatlantic respectively.
Among the other -only recent -finds of Polyplacophora, Leptochiton asellus is widely found from the Arctic to the Lusitanian. Hanleya hanleyi, Ischnochiton albus and the above-mentioned Tonicella marmorea are all found in the Subarctic, Boreal and Lusitanian regions. The last three species, Callochiton septemvalvis, Lepidochitona cinereus and Tonicella rubra, are all restricted to the Boreal-Lusitanian region.

Class Gastropoda Subclass Prosobranchia Order Archaeogastropoda
Scissurella crispata Fleming 1828 Fig. 6 Distribution. W Greenland, S and W Iceland, Spitsbergen, Norway north of Lofoten, and south to the Mediterranean.
Occurrence. The Subarctic (not in true Arctic water), Boreal and Lusitanian regions (according to Thorson 1941).
Habitat. In the waters around Iceland (Thorson 1941, p. 4), the living specimens have often been found at depths greater than 500 m on clay bottom. However, Poppe & Goto (1991, p. 64) write that the species lives on stones, shelly sand and clay bottoms between 15 and 600 m. Fretter & Graham (1976, pp. 2-4) stated that the species is always sublittoral, even in the extreme northerly limits of its range, and occurs from 8-2000 m. It is not recorded from Danish waters although Fretter & Graham mentioned it from the Norwegian and Swedish coasts of the Skagerrak.
Only subfossil finds. During the Eemian in the Kattegat region. Lacuna pallidula (da Costa 1778) Fig. 7a, b Distribution. From Spitsbergen, around Iceland and along the Atlantic coast down to the Gulf of Biscay. Enters the Danish waters, including the Limfjord, the Øresund and the Baelt Sea.
Habitat. Intertidal to 70 m deep on weeds.
Subfossil finds. The Baelt Sea, Limfjord, North Sea and Vendsyssel regions, Holocene. In the Skagen Well from the Subatlantic.

Lacuna crassior (Montagu 1803)
Distribution. From the Arctic Seas to the British Isles. Only records from the North Sea and from the NW coast of Sweden.
Occurrence. The Arctic, Subarctic and Boreal.

Lacuna parva (Montagu 1803)
Distribution. From Norway off the Lofoten, and south to Spain, found in the Kattegat region with fjords, but few records, and not found in the Limfjord.
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. From the North Sea during the Eemian.

Lacuna vincta (Montagu 1803)
Distribution. From W Greenland around Iceland, Norway and south to Spain. In the Danish waters, including the Limfjord, found into the Baelt Sea (Fretter & Graham 1980).
Subfossil finds. The Baelt Sea, Kattegat, Limfjord, North Sea and Vendsyssel regions, Holocene. In the North Sea region found during the Eemian. In the Vendsyssel area recorded from the Eemian, and also from the Early/Middle and Late Weichselian (Older and Younger Yoldia Sea respectively).

Hydrobia neglecta Muus 1963
Distribution. The British Isles, Ireland and the North Sea.

Occurrence. Boreal and Lusitanian.
Habitat. Shallow-water environments on the soft substratum or the vegetation.
Subfossil finds. None. Fig. 8 Distribution. Norway off Lofoten south to the Mediterranean. In all the Danish waters including the Baltic.

Occurrence. The Boreal and Lusitanian.
Habitat. The intertidal zone, but has been found as deep as 20 m, on soft substrate, most often on intertidal banks of firm mud or muddy sand (Fretter & Graham 1978a, p. 122).
Subfossil finds. The Baelt Sea, Baltic, Kattegat, Limfjord, North Sea and Vendsyssel regions, Holocene. In the Skagen Well from the Subatlantic. During the Eemian recorded from the Baelt Sea, Baltic, Kattegat and the North Sea regions.

Hydrobia ventrosa (Montagu 1803)
Distribution. Norway off Lofoten, south to the Mediterranean. In all the Danish waters including the Baltic.

Occurrence. The Boreal and Lusitanian regions.
Habitat. The intertidal zone, on soft substratum like Hydrobia ulvae, but prefers lower salinities (Fretter & Graham 1978a, p. 126). The two species may occur together, so quantitative analyses must be undertaken to designate any changes in the environment (Petersen 1993).

Potamopyrgus antipodarum (Gray 1853)
Distribution. From Scandinavia to Spain and in Danish waters into the Baltic, a late immigrant according to Jensen & Knudsen (1995).
Occurrence. The Boreal and Lusitanian regions. Habitats. In all kinds of brackish and freshwater habitats. Much like the distribution of Hydrobia ventrosa in brackish waters (Fretter & Graham 1978a, p. 132).

Skeneopsis planorbis (Fabricius 1780)
Distribution. W Greenland, around Iceland and Norway, south to the Mediterranean. Known from few places in Danish waters.
Habitat. Intertidal down to a depth of 70 m, lives on seaweeds.
Only subfossil finds. The Limfjord and the Vendsyssel regions, Holocene. Fig. 9 Distribution. From the Shetlands south into the Mediterranean.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Shallow waters, intertidal, lives on seaweeds on rocky shores.
Only subfossil finds. The Skagen Well from the Subatlantic.

Alvania abyssicola (Forbes 1850)
Distribution. From northern Norway to the Mediterranean. The species extends into the Skagerrak and Kattegat, including the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. On muddy bottom in sublittoral areas at depths of 15-100 m.
Subfossil finds. The Vendsyssel area from the Eemian.

Alvania jeffreysi (Waller 1864)
Distribution. S and W Iceland, Norway, south to the Mediterranean. Found in the Skagerrak, but not in the North Sea.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Always sublittoral from 50 to 600 m on sandy bottom.

Alvania lactea (Michaud 1830)
Distribution. From the Channel Islands south to Morocco and the Mediterranean.

Occurrence. The Lusitanian region.
Habitat. Sublittorally under stones and amongst algae.

Alvania cimicoides (Forbes 1844)
Distribution. SW and NW Iceland (empty shells), Norway, north of Lofoten, and south to the Mediterranean; probably absent from the Channel and the North Sea.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittoral, from the laminarian zone downwards, but mainly in deeper water down to 500 m. Habitat. Sublittoral to a depth of 60 m amongst algae and on sandy or gravelly bottoms.

Onoba aculeus (Gould 1841)
Distribution. From Spitsbergen, W Greenland, around Iceland and along the coast of Norway into the Kattegat, including the Øresund. Also found at localities off Ireland.
Habitat. Found to about 200 m on algae.

Onoba semicostata (Montagu 1803)
Distribution. Around Iceland, along the coast of Norway and south to the Mediterranean. Absent from the eastern North Sea coasts, but extends through the Limfjord and Kattegat, including the Øresund, into the Baelt Sea and the most saline parts of the Baltic (Fretter & Graham 1978b).
Habitat. From the intertidal region to depths of 100 m. Found under stones, amongst weeds, mussels and tunicates in shelly gravel, but only where there are quantities of silt (Fretter & Graham 1978b).

Onoba proxima (Forbes & Hanley 1850)
Distribution. From the western coast of Britain south to the Mediterranean.

Occurrence. The Lusitanian region.
Habitat. From 10 to 170 m on bottoms of muddy sand.
Only subfossil finds. The Limfjord region, Holocene. Fig. 10 Distribution. From Norway off Lofoten and south to the Mediterranean, extends through Skagerrak into the Kattegat, including the Øresund, but absent from the Limfjord.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Muddy bottoms at depths of 10-50 m in the northern parts of its range, but extending to 120 m in the south. Further notes on Onoba species in Fretter & Graham (1978b, p. 170).
Subfossil finds. The Kattegat, Limfjord, North Sea, Vendsyssel and Skagen areas, Holocene. In the Skagen Well recorded from the Atlantic, the Subboreal and the Subatlantic. During the Eemian recorded from the North Sea. Fig. 11 Distribution. From Norway off the Lofoten islands, and south to the Mediterranean, extending into the Limfjord and the Kattegat with the Danish fjords, including the Øresund and the Baelt Sea.

Occurrence. The Boreal and Lusitanian regions.
Habitat. On rocky shores amongst weeds, sublittoral to 15 m. It is tolerant of some brackishness (Fretter & Graham 1978b

Rissoa inconspicua Alder 1844
Distribution. From northern Norway, north of Lofoten, and south to the Mediterranean. Occurring in the Limfjord, Øresund and Baelt Sea.
Occurrence. The Boreal and Lusitanian regions. Fretter & Graham (1978b, p. 200) indicate that the species is found to the Arctic. However, it is not recorded from Iceland and the Faroes but only from Norway north of Lofoten (Thorson 1941, table II

Rissoa parva (da Costa 1779)
Distribution. From Norway, north of Lofoten and the Faeroes, south to the Mediterranean, found in the Limfjord (Petersen 1986a) and the northern part of the Øresund but not in the Baltic according to Fretter & Graham (1978b). However, Bondesen (1975 includes the species in the Baltic, but excludes it from the Baelt Sea. Petersen (1888, p. 93) regarded the species as being limited to the central part of the Kattegat, depending on sufficient salt content -therefore the information of the occurrences in the Baltic given by Bondesen (1975) is surprising.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to about 25 m on fronds, smaller weeds and under stones. In the Faeroes from the rock pools and the beach to a depth of 20 m (Spärck & Thorson 1931 , lab. no. 355,93. × 20. MGUH 25321. desen (1975) has Rissoa violacea sensu lato from the Skagerrak, the Kattegat and the Limfjord regions.

Occurrence. The Boreal and Lusitanian regions.
Habitat. In the tidal zone to about 50 m on weeds and amongst sandy gravel.
Subfossil finds. The Limfjord, North Sea, Vendsyssel and Skagen areas, Holocene. In Skagen recorded from the Subatlantic. The species occurred during the Eemian in the Kattegat region.

Assiminea grayana Fleming 1828
Distribution. The species is confined to the North Sea coasts. In Danish waters it extends south to Blåvands Huk.

Occurrence. The Boreal region.
Habitat. The species is limited to the upper parts of the salt-marsh areas on the vegetation.

Caecum glabrum (Montagu 1803)
Distribution. From Norway off Lofoten south to the Mediterranean. It extends into Kattegat, where it has been reported from the northern part (Jensen & Knudsen 1995), but not from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittorally to about 250 m on sandy and sandy-muddy bottoms.
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the Baelt Sea and the North Sea during the Eemian.

Tornus exquisitus (Jeffreys 1883)
Distribution. Within the Danish waters recorded from northern Kattegat (Jensen & Knudsen 1995), but no record is given by Fretter & Graham (1978b, p. 232) so the species is not treated further.
Habitat. Unknown for this species.
Subfossil finds. None. Fig. 13 Distribution. From off Lofoten in Norway south to the Mediterranean. It is found through the Skagerrak, Limfjord, Kattegat, including the Øresund, and into the Baelt Sea, but not from the southern coastal part of the North Sea.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Common in shallow sublittoral water, but recorded to 250 m. Found on soft bottoms in association with weeds.
Subfossil finds. The species is recorded from all regions during the Holocene. From Skagen recorded from the Subatlantic. From the Eemian found in the Baelt Sea, Kattegat, North Sea, and Vendsyssel regions. Occurrence. The Boreal-Lusitanian regions within its European distribution. Crepidula fornicata was transferred by man as seen also for species like Mya arenaria.

Turritella communis
Habitat. Sublittoral to depths of c. 10 m. The animals live in chains, the oldest attached to a substrate which might be an oyster. The species was actually transported to Europe with oysters (Fretter & Graham 1981, p. 311).

Capulus ungaricus (Linnaeus 1758)
Distribution. Empty shells recorded from SW and NW Iceland and living specimens from Norway north of Lofoten south to the Mediterranean. The record from Greenland mentioned in Fretter & Graham (1981) cannot be sustained in the literature (Thorson 1944b(Thorson , 1951.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Usually sublittorally to 805 m attached to stones or the host animal.
Subfossil finds. None (young date from the North Sea).

Lamellaria perspicua (Linnaeus 1758)
Distribution. SW and NW Iceland, Norway from Lofoten and south to the Mediterranean. It occurs in the Skagerrak but not on the Danish coasts.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone and downwards to depths of 1200 m, especially in the southern parts of its range on rocky shores and under stones.

Velutina plicatilis (Müller 1776)
Distribution. From East Greenland and Spitsbergen, southern and western Iceland, Norway north of Lofoten and south to northern Spain. It extends into the Skagerrak, Kattegat and the northern part of the North Sea.
Habitat. From 10 to c. 375 m deep on hard bottoms, usually in association with ascidians and hydroids.

Velutina velutina (Müller 1776)
Distribution. From Spitsbergen, E and W Greenland, around Iceland and Norway south to the Mediterranean. It extends into the Skagerrak and Kattegat, including Øresund.
Habitat. Sublittoral extending to 1000 m on hard bottoms associated with tunicates.

Trivia arctica (Pulteney 1799)
Distribution. From Norway off Lofoten and south to the Mediterranean. It extends into the Skagerrak and Kattegat (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittoral to about 100 m, in southerly latitudes to about 1000 m. It is associated with ascidians.

Trivia monacha (da Costa 1778)
Distribution. From the British Isles south to the Mediterranean. The recent distribution in the North Sea is questioned, and the species is not recorded from Scandinavia (Fretter & Graham 1981, p. 329 Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. Sublittorally to about 80 m deep on sandy clay bottoms.
Subfossil finds. None (late date from the North Sea). Fig. 16 Distribution. From southern and western Iceland and Norway off the Lofoten islands south to the Mediterranean (Thorson 1941). It extends into the Skagerrak, Kattegat and Øresund, but the species is not recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittoral between 10 and 50 m, extending to 2000 m. Infaunal on sandy shores, clean sand and some admixture of mud. According to Petersen (1888), it is common on mixed bottoms in the Kattegat. Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From 10 to 2000 m on clay bottoms -the greatest depths in the most southerly parts of its range (Fretter & Graham 1981). In Greenland waters common in the Arctic Macoma community (Thorson 1944b).
Subfossil finds. The Vendsyssel region during the Early/ Middle Weichselian and Late Weichselian (the Older and Younger Yoldia Sea respectively).

Natica affinis (Gmelin 1790)
Distribution. From Spitsbergen, W and E Greenland, around Iceland and Norway south to the Mediterranean. However, within the Lusitanian region the species lives in deep water (Fretter & Graham 1981, p. 345). The species is recorded from Danish waters (Jensen & Knudsen 1995).
Habitat. From about 4 m depth in high latitudes to well over 2000 m in low ones on sandy, muddy and clay bottoms. As mentioned for other species with a wide geographical distribution this is a 'tropical submerge' which is quite common for cold-water animals which in the northern regions inhabit the surface water to occur mainly or exclusively in deeper zones in the southern seas (Ekman 1953, p. 112).
The species is found in the Arctic Macoma community (Spärck 1937).
Subfossil finds. Recorded from the Vendsyssel area during the Early/Middle Weichselian (the Older Yoldia Sea), and the Late Weichselian (the Younger Yoldia Sea).

Triphora adversa (Montagu 1803)
Distribution. From Norway off the Lofoten islands and south to Spain. It extends into the Kattegat, including Øresund and the Baelt Sea, but not recorded from the Limfjord.
Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittorally to 100 m under stones, algae or associated with sponges.
Subfossil finds. The Baelt Sea, Kattegat, Limfjord, North Sea and Vendsyssel areas, Holocene. Recorded from the Baelt Sea and the North Sea during the Eemian.

Cerithiella metula (Lovén 1846)
Distribution. S and W Iceland, Norway north of Lofoten, and south to the Mediterranean. Recorded from the Danish waters (Jensen & Knudsen 1995), although rare in the Skagerrak and not occurring in the Kattegat (Fretter & Graham 1982, p. 377).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 40 to 400 m depth on soft bottoms.

Cerithiopsis barleei Jeffreys 1867
Distribution. According to Fretter & Graham (1982), from SW England south to the Mediterranean. However, the species is recorded from Danish waters, i.e. the Øresund area, although as rare (Jensen & Knudsen 1995), but is not found in the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittorally associated with sponges.

Cerithiopsis tubercularis (Montagu 1803)
Distribution. From Norway off the Lofoten islands and south to the Mediterranean. Recorded from the Swedish west coast, but not in Danish waters (Fretter & Graham 1982).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone and sublittorally to 100 m. The species is found on sponges.
Only subfossil finds. The Limfjord region, Holocene, and the North Sea during the Eemian.

Epitonium clathratulum (Kanmacher 1797)
Distribution. From Norway and south to the Mediterranean. It extends into the Kattegat, including the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 30 to 100 m deep on sandy-muddy bottoms.

Epitonium clathrus (Linnaeus 1758)
Distribution. From Norway off the Lofoten islands and south to the Mediterranean. The species extends into the Kattegat and Øresund (Jensen & Knudsen 1995), but does not enter the Danish fjords (Fretter & Graham 1982, p. 387).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittorally from 5 to 70 m on sandy-muddy bottoms.
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the Baelt Sea and the North Sea during the Eemian. Fig. 18 Distribution. From Norway off the Lofoten islands and south to the Mediterranean. The species extends into the Kattegat, including the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 30 to 200 m depth on sandy-muddy bottoms.
Subfossil finds. The Skagen area, Holocene, recorded from the Subboreal and the Subatlantic. Occurrence. The Boreal and Lusitanian regions.
Habitat. From 5 to 20 m deep on sandy-muddy bottoms.

Aclis ascaris (Turton 1819)
Distribution. From Norway off Lofoten and south to the Mediterranean. The species extends into the Skagerrak and Kattegat, including the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 10 to 50 m deep on soft sandy bottoms.
Subfossil finds. The North Sea, Holocene. Distribution. From Norway off the Lofoten islands and south to the Mediterranean. The species is recorded from the southern Kattegat and Øresund. Occurrence. The Boreal and Lusitanian regions.
Habitat. From 15 to 150 m deep on bottoms of sand, muddy sand or gravel.
Subfossil finds. The Limfjord, North Sea and Skagen areas, Holocene; in the Skagen Well recorded from the Atlantic, Subboreal and Subatlantic.

Aclis walleri Jeffreys 1867
Distribution. From Norway off the Lofoten islands and south to the Mediterranean. Recorded from north of Skagen (Petersen 1888) and the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. According to Fretter & Graham (1982), at greater depths than the other Aclis ssp. -down to 550 m on soft bottoms.

Eulima bilineata (Alder 1848)
Distribution. From Norway north of Lofoten, south to the Mediterranean. In the Danish waters recorded from the southern Kattegat.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 to 250 m deep on soft bottoms associated with ophiuroids.

Haliella stenostoma (Jeffreys 1858)
Distribution. Off West Greenland, around Iceland, Norway off the Lofoten islands, and south to the Mediterranean.
Habitat. Sublittoral from about 70 to 3000 m on soft bottoms. The species has its main occurrence at rather great depths (Thorson 1941), but is also recorded from Danish waters (Jensen & Knudsen 1995).
Subfossil finds. None. Fig. 20 Distribution. From the Kattegat and south to the Mediterranean.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittoral from 30 to 150 m on soft bottoms.
Subfossil finds. The Skagen area, Holocene, recorded from the Subatlantic.

Polygireulima monterosatoi (Monterosato 1890)
Distribution. Norway south of the Lofoten islands, and south to the Mediterranean.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 to 120 m deep on sandy muddy or gravelly bottoms. However, as Fretter & Graham (1982, p. 421) say: "presumably these animals attack echinoderms like their relatives, but which is not known".
Subfossil finds. None. Fig. 21 Distribution. From the west coast of Britain and Ireland to the Mediterranean.
Only subfossil finds. The Skagen area, Holocene, recorded from the Subboreal and the Subatlantic. Fig. 22a, b

Vitreolina philippii (Reyneval & Ponzi 1854)
Distribution. From Norway off the Lofoten islands and south to the Mediterranean. According to Petersen (1888), very common in Danish waters from the Skagerrak, the Kattegat and the Øresund, and the Baelt Sea, but not recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the lowest part of the tidal zone to a depth of 200 m on soft bottoms. Fretter & Graham (1982, p. 422) hold it as perhaps the most common local eulimid and like other eulimids an intermittent parasite of echinoderms.
Subfossil finds. The Limfjord, Vendsyssel and Skagen areas, Holocene, recorded from the Subatlantic in the Skagen Well. Occurring in the Eemian in the Vendsyssel region. Fig. 23 Distribution. From southern Norway south to the Mediterranean. The species has a record from the Limfjord (Petersen 1986a).
Habitat. From low in the tidal zone to 30 m deep on muddy and sandy bottoms.
Only subfossil finds. The Skagen Well area, Holocene, recorded from the Subatlantic. Fig. 24 Distribution. From Norway south to Iberia. The species is recorded from the Danish waters south into the Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 14 to 100 m on soft bottoms of muddy sand and gravel. The species is an intermittent ectoparasite (Fretter & Graham 1982).
Subfossil finds. The Skagen area, Holocene, recorded from the Atlantic and Subatlantic. Fig. 25 Distribution. From Norway off the Lofoten islands and south to the Mediterranean.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 16 to 135 m deep on muddy sand and gravel bottoms, an ectoparasite of holothurians.
Only subfossil finds. The Skagen Well area, Holocene, recorded from the Subboreal. Fig. 26 Distribution. From west and south Iceland, Norway off the Lofoten islands, and south to the Bay of Biscay.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 100 to 300 m deep on soft bottoms.
Only subfossil finds. The Skagen Well area, Holocene, recorded from the Subatlantic.

Occurrence. The Boreal and Lusitanian regions.
Habitat. The animals are confined to the surface of regular sea urchins (Fretter & Graham 1982, p. 431).
Occurrence. The Boreal region.

Nucella lapillus (Linnaeus 1758)
Distribution. W Greenland, around Iceland, Norway from north of Lofoten, and south to the Straits of Gibraltar. The species reaches into the Skagerrak, but it is uncommon in Danish waters (Fretter & Graham 1984). However, it occurs on breakwaters along the North Sea and Skagerrak coasts. There are a few records from the southern Kattegat and Øresund (Jensen & Knudsen 1995).
Habitat. Intertidal on rocky shores and extends, albeit rarely, to depths of 30 to 40 m. It avoids very weedy shores and seems to stand only limited reduction of salinity (Fretter & Graham 1984, p. 445).

Boreotrophon clathratus (Linnaeus 1767)
Distribution. Spitsbergen, E and W Greenland, around Iceland, the Faroes and the coast of Norway south to the Skagerrak and Kattegat.
Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From 8 m to over 1000 m on soft bottoms.

Boreotrophon truncatus (Ström 1768)
Distribution. Spitsbergen, E and W Greenland, around Iceland, Norway south to the Biscay. The species extends in to Danish waters south to the Øresund.
Habitat. From the laminarian zone to depths of about 200 m on bottoms of a stony, gravelly or muddy nature.

Ocenebra erinacea (Linnaeus 1758)
Distribution. From the southern coasts of Britain south to the Mediterranean. However, the few records from

Occurrence. The Lusitanian region.
Habitat. Sublittoral to 150 m deep on stony bottoms.

Trophonopsis barvicensis (Johnston 1825)
Distribution. W and S Iceland, Norway and south to the British Isles, and further south (France) at greater depths. In Danish waters from the Kattegat, including the Øresund, although rare (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittoral at a few metres' depth at the northern end of its range to 300-400 m at the southern end.

Buccinum undatum Linnaeus 1758
Habitat. Sublittorally to about 1200 m deep usually on soft bottoms.
Subfossil finds. The Kattegat, Limfjord, North Sea, Vendsyssel and Skagen areas, Holocene, recorded as a fragment from the Skagen Well from the Subatlantic. During the Eemian in the Kattegat, North Sea, and Vendsyssel regions. From the Vendsyssel area found during the Late Weichselian (the Younger Yoldia Sea).

Buccinum cyaneum Bruguière 1792
Distribution. Spitsbergen, W and E Greenland around Iceland and Norway north of Lofoten.
Occurrence. The Arctic, Subarctic and northern part of the Boreal regions.
Habitat. From 0 to 392 m on all sorts of bottoms -sand, clay, stones and algae (Thorson 1944b).
Only subfossil finds. From the Vendsyssel area recorded during the Late Weichselian (the Younger Yoldia Sea).

Colus gracilis (da Costa 1778)
Distribution. S and W Iceland (empty shells), Norway off the Lofoten islands and south to Portugal. The species extends into the Kattegat.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Usually from 30 to 800 m deep (less common and deeper in the south).

Colus jeffreysianus (Fischer 1868)
Distribution. From Norway south to the Mediterranean. The species extends through the Skagerrak to the Kattegat, including the northern part of the Øresund.

Colus sabini (Gray 1824)
Distribution. From W Greenland (empty shells) and S and W Iceland, northern North Sea and extending into the Skagerrak (Jensen & Knudsen 1995).
Occurrence. The Boreal region. (A Subarctic extension is not considered, since only empty shells have been found off W Greenland and no occurrences on N and E Iceland (Thorson 1941(Thorson , 1944b.) Habitat. From 35 to 1500 m deep on muddy bottoms.

Liomesus ovum (Turton 1825)
Distribution. From Greenland, the Faeroes and the coasts of Norway. According to Fretter & Graham (1984, p. 465), the species is not recorded from the Skagerrak or Kattegat; however, Jensen & Knudsen (1995) mentioned this species as occurring in Danish waters. Furthermore, the species Liomesus ovum cannot be found in Thorson (1944b), who has Buccinum ovum Middendorff, which is not the same according to Fretter & Graham (1962), and the occurrence off the Faeroes cannot be confirmed in Spärck & Thorson (1931).

Occurrence. The Boreal region with only uncertain outposts into the Subarctic and Lusitanian regions.
Habitat. From 70 to 400 m deep on soft bottoms.

Neptunea antiqua (Linnaeus 1758)
Distribution. From southern Norway south to the Bay of Biscay. The species extends into the Kattegat, Øresund (Jensen & Knudsen 1995), and the Baelt Sea as far east as Lübecker Bucht. The species has also been recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 15 to 1200 m on all kinds of bottom, mainly soft.

Neptunea despecta (Linnaeus 1758)
Distribution. From Spitsbergen, E and W Greenland, around Iceland and the coasts of Norway, south to the seas off Denmark according to Fretter & Graham (1984), but not mentioned by Jensen & Knudsen (1995) in their annotated check list of recent marine molluscs of Danish waters.
Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From 6 to 1400 m on soft bottoms.
Only subfossil finds. The Vendsyssel region during the Late Weichselian (the Younger Yoldia Sea).

Turrisipho moebii (Dunker & Metzger 1874)
Distribution. From the coasts of northern and southern Norway and the Faeroes (Sipho sarsi in Spärck & Thorson 1931). The species extends into the Skagerrak.
Occurrence. The Boreal region.

Habitat. From 200 m to 1000 m deep on soft bottoms.
Subfossil finds. None.

Hinia incrassata (Ström 1768)
Distribution. S and W Iceland, Norway north of Lofoten, and south to the Mediterranean (Thorson 1941). The species extends into the Kattegat and Øresund, although rare in this place (Jensen & Knudsen 1995), and it has not been found in the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Rocky coasts in the lower part of the tidal zone. Mainly found in the shallow sublittoral, but may extend to about 200 m. Distribution. From Norway off Lofoten and south to the Mediterranean. In Danish waters within the Limfjord and Kattegat with fjords, the Øresund and the Baelt Sea.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to about 15 m deep on soft bottoms.
Subfossil finds. The Baelt Sea, Baltic, Kattegat, Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. In the Skagen Well material recorded from the Subatlantic. From the Baelt Sea, Baltic, Kattegat, North Sea and Vendsyssel regions recorded from the Eemian.

Troschelia bernicensis (King 1846)
Distribution. From Norway north of Lofoten and south to the west coast of Scotland and the Dogger Bank. Recorded from Danish waters by Jensen & Knudsen (1995).

Occurrence. The Boreal and Lusitanian (northern part) regions.
Habitat. Lives on the continental shelves and upper slopes, between 90 and 2700 m (Poppe & Goto 1991).

Cytharella coarctata (Forbes 1840)
Distribution. From Norway off the Lofoten islands (Thorson 1941: Mangelia costata) and south to the Mediterranean. The species is recorded from the Skagerrak and Kattegat where it extends into the Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to 250 m deep on sandy bottoms.
Subfossil finds. The Vendsyssel area, Holocene. During the Eemian in the North Sea region.

Oenopota incisula (Verrill 1882)
Distribution. The species is known from the Boreal zone of the east coast of North America, and is com- Occurrence. The Arctic, Subarctic, and in North America into the Boreal regions.
Habitat. In the Canadian north-east region the species has been collected from 6-7 to 140 m deep on clay (Macpherson 1971).
Only subfossil finds. From the Vendsyssel region recorded during the Eemian and Early/Middle Weichselian (the Older Yoldia clay).

Oenopota trevelliana (Turton 1834)
Distribution. Spitsbergen, E and W Greenland, around Iceland (Thorson 1941: Bela trevelliana (Turton)), Norway from north of Lofoten, and south to the British Isles. The species extends south to the Kattegat, including Øresund.
Habitat. Sublittorally from 25 m to depths over 300 m on fine sand.

Oenopota violacea (Mighels & Adams 1842)
Distribution. E and W Greenland, Spitsbergen, around Iceland and south along the coast of Norway, but not reaching the British Isles (Thorson 1941).

Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From 1 m to 761 m on mud and stones.
Only subfossil finds. The Vendsyssel area during the Eemian.

Bela exarata G.O. Sars 1878
Distribution. E and W Greenland, Spitsbergen, around Iceland, the Faeroes, and Norway from north of Lofoten and west of Ireland. The species is also recorded west of Iceland, where it has been found at depths down to 2214 m (Thorson 1941).
Habitat. In the northern part of its range it belongs to the shallow-water species (Norway and E Greenland from 3 m) (Thorson 1941).
Only subfossil finds. From the Eemian in the Vendsyssel area.

Mangelia attenuata (Montagu 1803)
Distribution. From Norway off the Lofoten islands and south to the Mediterranean. The species extends into the Skagerrak and Kattegat, including the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 5 to 150 m deep on sand or clay bottoms.
Subfossil finds. None. Fig. 31 Distribution. From Norway off the Lofoten islands and south to the Mediterranean. The species extends into the Skagerrak and Kattegat, including the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittorally from 4 m to 60 m deep on bottoms of sand and sandy mud.
Subfossil finds. The Skagen area, Holocene, recorded from the Subatlantic in the Skagen Well cores. During the Eemian found in the Vendsyssel region.

Mangelia nebula (Montagu 1803)
Distribution. Norway off the Lofoten islands and south to the Mediterranean. The species is recorded a few times from the Kattegat and extends into the Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 10 to 50 m deep on sandy bottoms.

Raphitoma purpurea (Montagu 1803)
Distribution. From northern Norway off the Lofoten islands south into the Mediterranean.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 10 to 100 m deep on sandy, gravelly and stony bottoms.

Raphitoma asperrima (Brown 1827)
Distribution. From the coast of Norway south to the Mediterranean, extending into the Kattegat, including the Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 to 100 m deep on sandy bottoms.

Raphitoma leufroyi (Michaud 1821)
Distribution. From the coast of Norway off the Lofoten islands and south to the Mediterranean, extending into the Skagerrak and with a few records from the northern Kattegat (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to 150 m deep on sandy, shelly and stony bottoms.

Raphitoma linearis (Montagu 1803)
Distribution. SW and NW Iceland, Norway from north of Lofoten and south to the Mediterranean. The species extends into the Skagerrak and Kattegat and Øresund, although rare (Jensen & Knudsen 1995).
Occurrence. The Boreal and Lusitanian regions. Habitat. From 10 to 200 m deep on sandy, shelly and stony bottoms.
Subfossil finds. The Limfjord and Vendsyssel area, Holocene. During the Eemian found in the Vendsyssel area (the Turritella terebra zone in the Skaerumhede sequence).

Taranis borealis Bouchet & Warén 1980
Distribution. So far as known, this species is confined to waters off western Norway and the Skagerrak (Fretter & Graham 1984, p. 548).

Occurrence. The Boreal region.
Habitat. From 150 m to nearly 2000 m deep on soft bottoms.

Taranis moerchi (Malm 1861)
Distribution. From Norway north of Lofoten south to the Mediterranean, extending into the Kattegat.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 80 m deep near the northern limits of its range to over 2000 m elsewhere on soft bottoms.

Admete viridula (Fabricius 1780)
Distribution. Spitsbergen, E and W Greenland, around Iceland, empty shells from off the Faeroes, Norway from north of the Lofoten islands, and south to the northern borders of the North Sea. Included in the recent Danish fauna (Jensen & Knudsen 1995).

Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From a few metres to depths of 1000 m, the greatest depths in the south of its range (Fretter & Graham 1984, p. 507) on soft bottoms.
Subfossil finds. Recorded from the Early/Middle Weichselian (The Portlandia arctica zone in the Skaerumhede sequence) in the Vendsyssel region.

Omalogyra atomus (Philippi 1841)
Distribution. W Greenland, around Iceland and Norway, south to the Mediterranean. Known from only a few places in Danish waters.
Habitat. From the lower part of the shore to a depth of 20 m, occurring on seaweeds.

Brachystomia carozzai van Aartsen 1987
Distribution. From the southern part of Norway (Spärck & Thorson 1931) and south to the Mediterranean. The species extends into the Kattegat and Limfjord. As commented on by Fretter et al. (1986, p. 605) and Jensen & Knudsen (1995), the determination of these small snails living ectoparasitically on other marine organisms is still in progress, so the actual situation for the record of subfossil material should be taken with great precaution.
Vendsyssel regions, Holocene. From the North Sea region during the Eemian.

Odostomia scalaris MacGillivray 1843
Distribution. From southern Norway south to the Mediterranean. The species extends into the Limfjord, through the Kattegat, including the Øresund, and the Baelt Sea into the Kiel Bay (Fretter et al. 1986, p. 600).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Associated primarily with banks of Mytilus edulis, but also recorded from other hosts (Fretter et al. 1986, p. 600). Subfossil finds. The Limfjord and Skagen areas, Holocene, in the Skagen Well recorded from the Subatlantic.

Chrysallida eximia (Jeffreys 1849)
Distribution. SW and NW Iceland, Norway north of Lofoten, and south to western Scotland. There is no record from Danish waters.
Habitat. From 20 m to more than 1000 m, the greater depths in the southern part of its range, on soft gravelly bottoms.
Only subfossil finds. The Limfjord region, Holocene. From the Vendsyssel area during the Eemian.

Chrysallida indistincta (Montagu 1808)
Distribution. From Norway off the Lofoten islands (Thorson 1941) and south to the Mediterranean. It extends into the Kattegat and Øresund (Jensen & Knudsen 1995), but is not recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 7 to 100 m deep on sandy bottoms.
Subfossil finds. The Limfjord, North Sea and Vendsyssel areas, Holocene. Recorded from the North Sea during the Eemian.

Chrysallida obtusa (Brown 1827)
Distribution. From Norway off the Lofoten islands and south to the Mediterranean. The species extends into the Limfjord and through the Kattegat into the Øresund (Fretter et al. 1986, p. 562).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone in rock pools to 90 m deep in stony places, associated with oysters (Fretter et al. 1986, p. 562).

Chrysallida spiralis (Montagu 1803)
Distribution. From Norway north of Lofoten and south to the Mediterranean. According to Fretter et al. (1986, p. 574), the species extends into the Kattegat and Øresund, but it is absent from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to about 120 m deep, often abundant in the neighbourhood of tubes of sedentary polychaetes (Fretter et al. 1986).

Ebala nitidissima (Montagu 1803)
Distribution. From south of Norway to the Mediterranean. Recorded from the Kattegat region with fjords and the Øresund and the Baelt Sea regions as far as Kiel Bay (Fretter et al. 1986, p. 630), but absent from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 5 to 50 m deep on muddy sand or shelly bottoms.
Subfossil finds. The Limfjord and Vendsyssel regions, Holocene. From the Baelt Sea and North Sea areas during the Eemian.

Eulimella laevis (Brown 1827)
Distribution. From Norway off the Lofoten islands and south to the Mediterranean. It has not been recorded from Danish waters except the Øresund region (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 to 400 m deep on muddy sand.
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. Fig. 33 Distribution. From Norway off the Lofoten islands, but empty shells only off SW Iceland (Thorson 1941), and south to the Mediterranean. It extends into the Kattegat along the Swedish west coast (Fretter et al. 1986), but occurs in the Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 to 400 m deep on muddy sand or sand.
Subfossil finds. The Limfjord and Skagen areas, Holocene, recorded in the Skagen Well from the Atlantic and Subboreal. From the Vendsyssel area found during the Eemian.  (Fretter et al. 1986), and it is doubtful whether the Danish records actually refer to this species. Therefore, the species is here considered to be Lusitanian and should not be taken as present in the recent Danish fauna, although recorded by Jensen & Knudsen (1995).
Habitat. From 30 to 60 m deep in gravelly or sandy mud.

Ondina diaphana (Jeffreys 1848)
Distribution. According to Spärck & Thorson (1931), present from southern Norway and south to the Mediterranean. In Danish waters the Kattegat and the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 to 90 m deep on soft bottoms.
Subfossil finds. The Limfjord and North Sea regions, Holocene.

Liostomia afzelii Warén 1991
This species, newly established, will not be considered further.

Odostomia acuta Jeffreys 1848
Distribution. From Norway north of Lofoten and south to the Mediterranean. The species is found in the Skagerrak, Kattegat and Øresund (Fretter et al. 1986, p. 613).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 to 30 m deep. Perhaps associated with bryozoans.

Odostomia conoidea Winckworth 1932 Fig. 34
Distribution. From Norway off the Lofoten islands and south to the Mediterranean. Recorded from the Skagerrak (Fretter et al. 1986) and the Øresund (Jensen & Knudsen 1995), but not from the Limfjord (Petersen 1986a).
Subfossil finds. The Baelt Sea, Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. In the Skagen area recorded from the Subatlantic.

Odostomia turrita Hanley 1844
Distribution. From Norway north of Lofoten and south to the Mediterranean. The species extends through the Kattegat to the Øresund (Fretter et al. 1986, p. 612), but is not recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to 100 m deep on weed and clay bottoms.
Subfossil finds. The Limfjord and Vendsyssel regions, Holocene. Recorded from the Vendsyssel area during the Eemian.

Odostomia albella Lovén 1846
Distribution. Empty shells recorded from Spitsbergen, SW and NW Iceland, Norway north of Lofoten and south to the Mediterranean. The species occurs in the Skagerrak (Fretter et al. 1986), the Øresund area (Jensen & Knudsen 1995), and the Limfjord region (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to depths of about 100 m on boulders, associated with growth of Pomatoceros (Fretter et al. 1986).
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. From the North Sea region during the Eemian.
Subfossil finds. The Limfjord and Vendsyssel regions, Holocene. Fig. 35 Distribution. From southern Norway (Spärck & Thorson 1931) to the British Isles. The species extends to the Swedish west coast but not further into the Kattegat (Fretter et al. 1986, p. 620).
Subfossil finds. The Skagen area, Holocene, recorded from the Atlantic and Subatlantic.

Turbonilla crenata (Brown 1827)
Distribution. From Norway off the Lofoten islands (Thorson 1941) and south to the Mediterranean. The species extends into the Kattegat and Øresund (Fretter et al. 1986), but is absent from the Limfjord (Petersen 1986a).
Occurrence. The Boreal and Lusitanian regions.  Distribution. From the south-western part of the British Isles to the Mediterranean (Fretter et al. 1986, p. 636). However, recorded from the northern Kattegat and northern Øresund although, rare (Jensen & Knudsen 1995).
Subfossil finds. The Limfjord, North Sea and Skagen regions, Holocene. From the Skagen area recorded from the Subatlantic.

Turbonilla lactea (Linnaeus 1758)
Distribution. From northern Norway and south to the Mediterranean. Present although uncommon in Danish waters (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to depths of about 80 m, occurring under stones in silty places in the tidal zone and on soft, muddy and sandy bottoms sublittorally (Fretter et al. 1986, p. 634).
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the Baelt Sea, Kattegat, and North Sea regions during the Eemian.

Acteon tornatilis (Linnaeus 1758)
Distribution. W and S Iceland, Norway off the Lofoten islands and south to the Mediterranean (Lemche 1938). The species extends into the Kattegat, including the Øresund (Petersen 1888, p. 78), but it is not recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone down to 250 m in sand, usually in sheltered areas (Poppe & Goto 1991, p. 192).
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the North Sea and Vendsyssel areas during the Eemian.

Haminoea navicula (da Costa 1778)
Distribution. From the British Isles south to the Mediterranean.
Only subfossil finds. The Baelt Sea, Kattegat, and North Sea regions during the Eemian.

Cylichna cylindracea (Pennant 1777)
Distribution. W and S Iceland, Norway off the Lofoten islands and south to the Mediterranean. The species extends into the Limfjord and Kattegat, including Øresund (Petersen 1888, p. 78; Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 40 to 200 m deep, in sand. According to Lemche (1938) associated with the Boreal Amphiura filiformis community in deeper water south of Iceland, corresponding to its occurrence in Danish waters.
Subfossil finds. The Limfjord and Vendsyssel regions, Holocene. Distribution. W and E Greenland, around Iceland, Norway north of Lofoten and south to the Bay of Biscay at greater depth (Lemche 1938, p. 9). The species extends into the North Sea and Skagerrak (Lemche 1928, p. 4).
Habitat. According to Lemche (1928), this species is also widely distributed in depth, being found in low water to depths down to 2700 m, on clay bottom (Faeroes).
Subfossil finds. The Limfjord, North Sea and Skagen areas, Holocene. In the Skagen Well recorded from the Subatlantic. Also found in the Vendsyssel area from the Early/Middle and Late Weichselian (the Older and Younger Yoldia Sea respectively).
Occurrence. The Arctic, Subarctic and Boreal (northernmost part) regions. Will be referred as an Arctic and Subarctic species.
Habitat. From 10 to 388 m deep (Iceland), especially found within the Macoma calcarea community, and might also occur within the Yoldia hyperborea community (Lemche 1938).
Only subfossil finds. Recorded from the Kattegat region during the Early/Middle Weichselian and the Vendsyssel region during the Early/Middle and Late Weichselian (the Older and Younger Yoldia Sea respectively).

Scaphander lignarius (Linnaeus 1758)
Distribution. From S and W Iceland, the Faeroes, Norway off the Lofoten islands and south to the Mediterranean.
Occurrence. The Boreal and Lusitanian regions.
Habitat. From 60 to 700 m deep. The species is associated with the Boreal Spisula elliptica community on sandy plateaus south and west of Iceland (Lemche 1938, p. 7).

Scaphander punctostriatus (Mighels & Adams 1841)
Distribution. E and W Greenland, S and W Iceland, the Faeroes, Norway north of Lofoten and south to the Mediterranean.
Habitat. Recorded from depths between 10 and 3000 m, this probably having some relation to its wide horizontal distribution. Around the Faeroes the species may be expected to be found on the great, sandy plateaus (Lemche 1928, p. 4).

Philine aperta (Linnaeus 1767)
Distribution. From the Faeroes, western Norway off Lofoten, and south to the Mediterranean (Lemche 1928). The species extends through Kattegat and Øresund, into the Baelt Sea as far as Kieler Bugt (Petersen 1888, p. 83), and it is also recorded from the Limfjord (Petersen 1986a).
Habitat. The species prefers shallow water but has been found at depths down to 100 m off the Faeroes (Lemche 1928) on sandy bottoms. In Danish waters recorded from 10 to 30 m, also on sandy bottoms (Petersen 1888).
Subfossil finds. The Limfjord and Vendsyssel regions, Holocene. Recorded from the Baelt Sea and the North Sea during the Eemian.

Philine angulata Jeffreys 1867
This species is mentioned by Jensen & Knudsen (1995), but only on the basis of one broken shell found in the Zoological Museum in Copenhagen; difficult to identify; occurrence uncertain. So in the light of "the difficult problem of the relation between punctata and angulata", as treated by Lemche (1948, p. 67), this find will be omitted, also that no subfossil species have been found. Fig. 38 Distribution. From Norway off the Lofoten islands and south to the Mediterranean.

Habitat. From low water-mark to 76 m (Forbes & Hanley 1853)
Subfossil finds. The Skagen region during the Eemian.

Philine denticulata (Adams 1800)
Distribution. From Norway south to the Mediterranean.
Occurrence. The Boreal and Lusitanian regions.

Philine punctata (Adams 1800)
Distribution. The Faeroes, southern part of the west coast of Norway, and south to the Mediterranean. Lemche (1928) also mentioned occurrences from Greenland, which, however, was not repeated in later papers (Lemche 1941a, b). Jensen & Knudsen (1995) report occurrences from the Øresund, although rare, and Petersen (1888) has a single find from the Baelt Sea and Petersen (1986a) from the Limfjord.

Occurrence. The Boreal and Lusitanian regions.
Habitat. At the Faeroes the species is recorded from depths down to 240 m (Lemche 1928).

Philine quadrata (Wood 1839)
Distribution. W Greenland, around Iceland, Norway north of Lofoten, and south to the Mediterranean. Recorded from the Øresund, but rare (Jensen & Knudsen 1995).
Habitat. The vertical range of the species is about 35 m down to 2150 m (Lemche 1938).

Philine scabra (Müller 1776)
Distribution. S and W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean. The species extends into the Kattegat, including the Øresund (Petersen 1888, p. 84).

Philinoglossa helgolandica Hertling 1932
Distribution. From the North Sea -Helgoland -and south to the Mediterranean, the species might occur in Danish waters (Jensen & Knudsen 1995, p. 29).

Diaphana minuta Brown 1827
Distribution. E and W Greenland, around Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean. The species extends into the Kattegat and Øresund (Petersen 1888; Jensen & Knudsen 1995).
Habitat. In general from the tidal zone to 770 m, but is said to prefer sandy clay at depths of 20-40 m (Lemche 1928). This is very much the same as for the Kattegat, where Petersen (1888) says that the species prefers mixed bottom at a depth of about 19-38 m.

Retusa obtusa (Montagu 1803)
Distribution. E and W Greenland, around Iceland, the Faeroes, Norway north of Lofoten, and south to the British Isles (Shetland and Scotland) (Lemche 1928). The species is found in the Limfjord and is common in the fjords and bays bordering the Kattegat, including the Øresund, and extends into the Baelt Sea and the western part of the Baltic (Petersen 1888, p. 81).

Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From the intertidal zone down to 300 m deep in mud or fine sand. In Danish waters Petersen (1888) points to the observed differences in depth, i.e. in the Kattegat region around 20 m while 60 m deep in the Baltic. The species is connected with the Arctic Macoma community (Lemche 1941a, b).
Subfossil finds. The Baelt Sea, Kattegat, Limfjord, North Sea and Vendsyssel regions, Holocene. Also recorded from the Vendsyssel area during the Early/Middle Weichselian and the Late Weichselian (the Older Yoldia Sea and the Younger Yoldia Sea respectively). Fig. 39 Distribution. The Faeroes, Norway north of Lofoten, and south to the Mediterranean (Lemche 1928(Lemche , 1938. The species extends through the Kattegat, including the Øresund, and into the Baelt Sea, and it is also recorded from the Limfjord (Petersen 1888, p. 80).

Rhizorus acuminatus (Bruguière 1792)
Distribution. From western and southern Norway south to the Mediterranean, in Danish waters from the southern Kattegat.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to 800 m deep.

Akera bullata O.F. Müller 1776
Distribution. The Faeroes, Norway north of Lofoten, and south to the Mediterranean (Lemche 1928). The species extends into the Limfjord, the Kattegat, including the Øresund, and the Baelt Sea as far as the Kieler Bugt (Petersen 1888).

Occurrence. The Boreal and Lusitanian regions.
Habitat. In sheltered bays down to 370 m deep (Poppe & Goto 1991). Common in shallow water with Zostera (Petersen 1888).
Subfossil finds. The Baelt Sea, Kattegat, Limfjord and Vendsyssel regions, Holocene. In the Baelt Sea and Kattegat regions recorded from the Eemian.

Order Thecosomata
Limacina retroversa (Fleming 1823) Fig. 41 Distribution. E and W Greenland, around Iceland, Norway north of Lofoten, and south to Ireland (Lemche 1938). It is common in the North Sea and Skagerrak, penetrating into the Kattegat, occasionally even into the Baelt Sea (Kramp 1961).

Habitat. Pelagic.
Subfossil finds. Recorded from the Vendsyssel and Skagen regions during the Eemian and from the Vendsyssel region during the Late Weichselian (the Younger Yoldia Sea).  Occurrence. The Arctic, Subarctic, Boreal and Lusitanian (northern part) regions.

Habitat. Pelagic.
Subfossil finds. Recorded (imprint) from the Skagen Well during the Late Weichselian (the Younger Yoldia Sea).

Ovatella myosotis (Draparnaud 1801)
Distribution. From Scandinavia along the coast of western Europe, south to the Mediterranean (Steenberg 1911, p. 204). In Danish waters recorded from the Baelt Sea and the Baltic (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Lives on sea wrack along the coasts (Steenberg 1911).
Occurrence. The Boreal and Lusitanian regions.   Distribution. E and W Greenland, N and E Iceland (Knudsen 1949b), the Faeroes, Norway north of Lofoten, and south to Portugal. The species might be found in Norske Rende. In Norway often found in glacial deposits (Muus 1959).
Occurrence. The main areas are the Arctic, Subarctic and Boreal regions, but the species extends into the Lusitanian region.
Only subfossil finds. Recorded from the Skagen Well in the Late Weichselian (the Younger Yoldia Sea) and from the Eemian. Fig. 45 Distribution. From northern Norway south to the Bay of Biscay and the Mediterranean. From Danish waters in the North Sea and Skagerrak (Muus 1959).

Occurrence. The Boreal and Lusitanian regions.
Habitat. It is a deep-water species preferring mud bottoms (Poppe & Goto 1993). In the Danish waters known from 100 to 480 m on mixed bottom (Muus 1959) connected with the Amphilipis norvegica/Pecten vitreus community at depths of 250-700 m.
Subfossil finds. Recorded from the Skagen Well during the Eemian.

Antalis agile G.O. Sars 1878
Distribution. S and W Iceland, Norway off the Lofoten islands, and south to the Mediterranean. In the Danish waters the species extends from the North Sea into the Skagerrak and Kattegat.  Occurrence. Mainly the Lusitanian region.
Habitat. Sublittorally from 1 m and down to 50 m on mud and sandy bottoms.
Only subfossil finds. Recorded from the Skagen Well during the Eemian.   Occurrence. The Arctic, Subarctic, Boreal and Lusitanian regions.

Nucula nitidosa Winckworth 1930
Habitat. From off-shore down to 300 m on muddy bottoms (Poppe & Goto 1993). The species is more littoral in the northern latitudes than in the south (Jensen & Spärck 1934).
Subfossil finds. From the Limfjord and North Sea regions, Holocene. Recorded from the Vendsyssel area during the Eemian, and from the Kattegat and Vendsyssel area during the Early/Middle Weichselian (the Older Yoldia Sea), and furthermore from the Vendsyssel region during the Late Weichselian (the Younger Yoldia Sea). Fig. 49 Distribution. SE and W Greenland, around Iceland, the Faeroes, Norway north of Lofoten, and south to the British Isles. According to Ockelmann (1958), lacking in the most high-Arctic seas. In south-western Europe only at depths greater than 400 m (Madsen 1949). The species extends from the North Sea and Skagerrak into the Kattegat and Øresund (Jensen & Spärck 1934).   Fig. 51 Distribution. E and W Greenland, Spitsbergen, around Iceland and Norway north of Lofoten (Madsen 1949).
Habitat. From about 5 to 675 m on clay or mud, in few cases sand (Madsen 1949).
Only subfossil finds. Recorded from the Vendsyssel and Skagen areas during the Early and Middle Weichselian (the Older Yoldia Sea) and from the Skagen Well also during the Late Weichselian (the Younger Yoldia Sea). Fig. 52 Distribution. According to Ockelmann (1958, p. 26): "Widely distributed in high-Arctic seas".
Habitat. From 2 m to 340 m deep, however, the species is most common at depths between 10 and 50 m on a muddy or clayey bottom (Ockelmann 1958, p. 25 Subfossil finds. None.

Malletia obtusa (G.O. Sars 1872)
Distribution. From Norway off the Lofoten islands and south to SW Europe. The occurrences around the British Isles and in the Mediterranean are at depths greater than 400 m (Madsen 1949).

Occurrence. The Boreal and Lusitanian regions.
Habitat. This species has a wide range of depths according to Madsen (op. cit.) from 20-3200 m deep. In Danish waters only from the deeper part (> 300 m), and in the Skagerrak mostly at a depth of 600 m (Jensen & Spärck 1934).

Acar nodulosa (Müller 1766)
Distribution. S and W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean. The species has been taken on the Dogger Bank, but not in the inner Danish waters.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone down to 1000 m fixed with its byssus to hard substrates (Poppe & Goto 1993).
Subfossil finds. None. Fig. 55 Distribution. W and E Greenland, Spitsbergen, and around Iceland. The occurrences from SW Europe are of dead shells and from deep water (Ockelmann 1958).

Bathyarca glacialis (Gray 1824)
Occurrence. Mainly the Arctic and Subarctic regions; however, the occurrences from southern Iceland imply extension into the Boreal region as well.
Habitat. From 6-10 m down to 425 m (East Greenland), but most abundant below 40 m on clay bottoms with stones and gravel, where the Astarte crenata community occurs.
Only subfossil finds. Recorded from the Vendsyssel (not in the Skaerumhede sequence) and Skagen regions during the Early/Middle Weichselian and the Late Weichselian respectively.

Bathyarca pectunculoides (Scacchi 1834)
Distribution. W and E Greenland, around Iceland, Norway north of Lofoten, and south to the Mediterranean.
In the Danish waters the species is rather common in the deeper part of the Skagerrak between 300-700 m (Jensen & Spärck 1934). Occurrence. The Arctic, Subarctic, Boreal and Lusitanian regions.
Habitat. From 50 m (the Shetland Isles) to more than 2000 m (the Mediterranean) (Madsen 1949).

Distribution. A Mediterranean species according to
Jensen & Spärck (1934) but also found in the neighbouring Atlantic (Poppe & Goto 1993).
Only subfossil finds. The Eemian in the Kattegat and North Sea regions.

Mytilaster solidus form minimus (Poli 1795)
Distribution. From Bretagne and south into the Mediterranean.
Habitat. Intertidal, attached to rocks or algae.
Subfossil finds. Recorded from the Baelt Sea during the Eemian.

Modiolula phaseolina (Philippi 1844)
Distribution. From SW and NW Iceland, the Faeroes, Norway north of Lofoten, and south to the British Isles (Petersen 1968) and the Mediterranean. The species extends from the North Sea and Skagerrak into the Kattegat and Øresund (Jensen & Knudsen 1995), but is not recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone and down to 160 m, attached by its byssus to rocks or on the base of the larger seaweeds (Poppe & Goto 1993), but also recorded from depths of 1000 m.

Musculus laevigatus (Gray 1824)
Distribution. E and W Greenland, around Iceland and Norway north of Lofoten.
Occurrence. The Arctic, Subarctic and Boreal regions.

Habitat. From the infralittoral zone down to 83 m (Poppe & Goto 1993).
Only subfossil finds. Recorded from the Early/Middle Weichselian (the Older Yoldia Sea, but not in the Skaerumhede sequence) and the Late Weichselian (the Younger Yoldia Sea) in the Vendsyssel region.
Habitat. As mentioned by Poppe & Goto (1993, p. 48): "The species has been collected repeatedly on the skulls of whales, where it lies, attached in the sutures, by its byssus".

Occurrence. The Subarctic and Boreal regions.
Habitat. Around Iceland one of the most common bivalves present from nearly all localities along the NW, N and E coast, both in the fjords and on the outer part of the shelf, at depth from a few metres to 300 m (Madsen 1949). Occurrence. The Subarctic, Boreal and Lusitanian regions.
Habitat. Between 30 and 600 m, fixed by its byssus to hard substrates (Poppe & Goto 1993). The species lives in the deeper part of the Skagerrak, from 400 to 600 m, according to Jensen & Spärck (1934).
Subfossil finds. The Limfjord, Holocene. Recorded from the Eemian in the Skagen Well. Fig. 60 Distribution. E and W Greenland, N and E Iceland, Spitsbergen, and Norway north of Lofoten (Madsen 1949). However, at depths greater than 400 m the species has been found off the Faeroes and the British Isles.
Habitat. In the Arctic seas living in shallow water from 5 m, but most common between 20 and 70 m on clay bottoms containing stones or shells (Ockelmann 1958).
Only subfossil finds. Recorded from the Vendsyssel region and the Skagen Well during the Early/Middle Weichselian (the Older Yoldia Sea).

Palliolum striatum (Müller 1776)
Distribution. From S and W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean. The species extends from the North Sea and Skagerrak into the Kattegat, including Øresund.
Occurrence. The Boreal and Lusitanian regions.
Habitat. From shallow water around 5 m to more than 800 m deep on all types of bottom (Poppe & Goto 1993). The vertical range off Iceland is indicated to lie between 100 and 260 m (Madsen 1949).

Palliolum tigerinum (Müller 1776)
Distribution. From NW, W and S Iceland, the Faeroes, Norway north of Lofoten, and south to Morocco. In Danish waters from the North Sea and Skagerrak into the Kattegat, including the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone down to 400 m, but deeper in the southern part of its range on sandy bottoms (Poppe & Goto 1993).

Pecten maximus (Linnaeus 1758)
Distribution. Norway off the Lofoten islands and south to Spain. In Danish waters rarely found living in the Kattegat and only shells have been recovered from the Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone down to 250 m on sand and gravel bottoms (Poppe & Goto 1993).

Pseudamussium septemradiatum (Müller 1776)
Distribution. S Iceland, Norway from north of the Lofoten islands, and south to the Mediterranean. In Danish waters the species extends from the Skagerrak and becomes common in the southern Kattegat with finds also in the Øresund (Jensen & Spärck 1934;Jensen & Knudsen 1995).
Occurrence. The Boreal and Lusitanian regions.
Habitat. In general living between 60 and 600 m deep on muddy bottoms (Poppe & Goto 1993). In Danish waters often found between 30 and 60 m.
Subfossil finds. Recorded from the Vendsyssel region during the Eemian.

Similipecten similis (Laskey 1811)
Distribution. S and W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean (Petersen 1968). The species extends into the Kattegat from Skagerrak.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Sublittorally between 4 and 250 m deep on sand and fine gravel bottoms (Poppe & Goto 1993 Subfossil finds. None.

Anomia ephippium Linnaeus 1758
Distribution. From the British Isles, including the Orkney Islands, and south to the Mediterranean.

Occurrence. Mainly the Lusitanian region.
Habitat. From the intertidal zone down to 150 m on all kinds of hard substrates.
Only subfossil finds. The Limfjord and the Vendsyssel region, Holocene. Fig. 61 Distribution. Around Iceland, the Faeroes, Norway north of Lofoten, and south to the Bay of Biscay. The species extends into the Kattegat, Øresund, and occurs in the Limfjord (Jensen & Spärck 1934).
Habitat. From 5 to 110 m deep fixed on hard substrates, but also on algae and crustaceans (Poppe & Goto 1993).
Subfossil finds. The Kattegat, Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. From the Skagen Well recorded from the Subatlantic. During the Eemian recorded from the Baelt Sea and the North Sea regions.

Crassostrea gigas (Gmelin 1791)
This oyster species from the Portuguese-Spanish region (Poppe & Goto 1993) has been introduced in 1972 as spat for commercial production (Jensen & Knudsen 1995) and is not considered here, although mentioned as now part of the Danish molluscan fauna.

Chama gryphoides Linnaeus 1767
This Lusitanian species (up to the coasts of Portugal) has only one record from Danish waters (Jensen & Knudsen 1995), and this is considered to have been dropped by a ship. Therefore it will not be discussed.

Lucinella divaricata (Linnaeus 1758)
Distribution. From the English Channel and southern part of the North Sea south to the Mediterranean.

Occurrence. Mainly the Lusitanian region.
Habitat. From the tidal zone down to a depth of 60 m in fine sand and/or mud (Poppe & Goto 1993).
Only subfossil finds. The Eemian in the Baelt Sea, Kattegat, and North Sea regions.

Lucinoma borealis (Linnaeus 1758)
Distribution. The Faeroe islands, Norway from off Lofoten, and south to the Mediterranean (Petersen 1968). In Danish waters the species occurs in the Kattegat, including the Øresund, but is not recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone down to 500 m deep on gravel bottoms and in pure sand and/or mud (Poppe & Goto 1993). In Danish waters between 20 and 50 m (Jensen & Spärck 1934).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 7 to 250 m deep on sand, mud and gravel bottoms (Poppe & Goto 1993).

Axinopsida orbiculata (G.O. Sars 1878)
Distribution. E and W Greenland, around Iceland, the Faeroes, and Norway north and just south of the Lofoten Islands (Petersen 1968). The species occurs off the north western part of Scotland.
Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From 2 to 50 m deep on sand, clay and mud around Iceland (Madsen 1949). North of the Hebrides occurring at depths down to 900 m (Jensen & Spärck 1934).
Only subfossil finds. The Vendsyssel region from the Early and Middle Weichselian (the Older Yoldia Sea) and the Late Weichselian (the Younger Yoldia Sea).

Thyasira croulinensis (Jeffreys 1847)
Distribution. W Greenland, around Iceland, the Faeroes, Norway north of Lofoten (Petersen 1968), and south to the Mediterranean (Poppe & Goto 1993). In Danish waters taken in the North Sea and Skagerrak.
Habitat. About 40 to 2500 m off the Faeroes on gravel and clay (Petersen 1968). In Danish waters the species is found in the deeper water (Jensen & Spärck 1934).

Thyasira equalis (Verrill & Bush 1898)
Distribution. It is questioned by Nordsieck (1969, p. 79) if T. equalis should be Thyasira flexuosa var. rotunda. There are no subfossil finds under the name of T. equalis, so this species will not be considered any further. However, as discussed by Ockelmann (1958, p. 100) a species, T. equalis, does occur in the Arctic, while T. flexuosa has a Boreo-Lusitanian main distribution. Fig. 63 Distribution. E and W Greenland, Spitsbergen, around Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean. In the Danish waters it is very common and extends into the Øresund (Jensen & Knudsen 1995), but is not recorded from the Limfjord (Petersen 1986a). and Skagen regions, Holocene. From the Skagen Well recorded from the Subatlantic. From the North Sea during the Eemian and in the Vendsyssel region recorded from the Late Weichselian (the Younger Yoldia Sea).

Thyasira sarsi (Philippi 1845)
Distribution. From Novaja Semlja along the coast of Norway south to the Skagerrak region. The species extends into the Kattegat, including the Øresund (Jensen & Knudsen 1995).
Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From 100 m to deep water.

Leptaxinus ferruginosus (Forbes 1844)
Distribution. W Greenland, W Iceland, Spitsbergen, Norway off the Lofoten islands, and southwards to Madeira (Madsen 1949). Jensen & Spärck (1934) mentioned the species from the deeper part of the Skagerrak, but Jensen & Knudsen (1995) have no further record of this species as belonging to the recent Danish fauna.
Habitat. About 20 m to more than 3000 m. The vertical range off Iceland is 320-560 m. So here is another example of tropical submerge (see Order Mesogastropoda Natica affinis).
Subfossil finds. Recorded from the Vendsyssel region during the Eemian. Fig. 64 Distribution. Around Iceland, the Faeroes, Norway from north of Lofoten, and south to West Africa (Petersen 1968). The species has a common distribution in Danish waters, including the Limfjord, south to the Baelt Sea by Warnemünde (Arntz et al. 1976), and the Øresund (Jensen & Spärck 1934). Also found in the North Sea (Petersen 1977).
Habitat. Intertidal zone down to 2500 m, often in commensal association with other animals. In the North Sea it is recorded from 20 to 90 m as a commensal on for example, Acrocnida brachiata (Petersen 1977).
Subfossil finds. The Baelt Sea, Kattegat, Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. From the Skagen Well, records from the Preboreal-Boreal, Subboreal and Subatlantic. From the Baelt Sea, Baltic, North Sea and Vendsyssel regions also recorded from the Eemian.

Mysella tumidula (Jeffreys 1867)
Distribution. This species is recorded by Jensen & Knudsen (1995) as being part of the Danish fauna, although it seems to have a purely Lusitanian distribution (Poppe & Goto 1993). The species has no subfossil occurrence.

Montacuta substriata (Montagu 1803)
Distribution. W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean. In Danish waters rarely found in the North Sea, Skagerrak and Kattegat.

Occurrence. The Boreal and Lusitanian regions.
Habitat. Off Iceland the vertical range is between 31 and 165 m (Madsen 1949). In Danish waters out to depths of around 700 m (Skagerrak) reported as a commensal on Spatangus purpureus (Jensen & Spärck 1934) and from the North Sea also on Echinocardium flavesens at depths from 30 to 100 m (Petersen 1977).
Habitat. In general the species is most common just below the tidal zone, which according to Poppe & Goto (1993) is the preferred habitat of Echinocardium with which T. ferruginosa is often associated. However, the species is also found on Brissopsis lyrifera or living by itself (Jensen & Spärck 1934). Accordingly, the depth range may vary, around Iceland being between 32 and 80 m (Madsen 1949).
Subfossil finds. The Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. The records from the Skagen Well are from the Subboreal and Subatlantic. Furthermore, the species has been recorded from the Baelt Sea and North Sea during the Eemian.

Mysella dawsoni (Jeffreys 1864)
Distribution. Petersen (1888, p. 154) mentioned a single find from the Limfjord, and the species is mentioned by Petersen (1986a) on the basis of the tables on molluscan finds in the Limfjord from Danmarks Fiskeri-og Havundersøgelser (Petersen 1976). However, it is not cited among the recent Danish species by Jensen & Knudsen (1995). The species is mentioned from W Greenland (Thorson 1951) and south to the Mediterranean (Poppe & Goto 1993), and also from Spitsbergen and the west coast of Norway (Jensen & Spärck 1934).
Habitat. Deep-living species, but mentioned from a depth of 5 m by Posselt & Jensen (1898) and in sandy bottom in West Greenland.

Tellimya tenella (Lovén 1846)
Cited only from the Kattegat, including the Øresund, by Jensen & Knudsen (1995). No subfossil finds. Will not be considered further. Fig. 66 Distribution. W Greenland, around Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean.
Habitat. Lives in the tidal zone among plants and algae on rocks (Poppe & Goto 1993). Off Iceland in the tidal zone all around the island, but also down to a depth of 50 m (Petersen 1968).
Only subfossil finds. The Limfjord, Vendsyssel and Skagen regions, Holocene. Recorded from the Subatlantic in the Skagen Well.
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the Eemian in the Baelt Sea and North Sea areas.

Lepton squamosum (Montagu 1803)
Distribution. From the west coast of Norway and south to Spain. Only shells have been found in Danish waters (northern Kattegat) mentioned by Jensen & Knudsen (1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 10 to 120 m deep it lives in and around the burrows of the crustaceans (Upogebia deltaura and U. stellata) on mud or gravel bottoms (Poppe & Goto 1993).

Devonia perrieri (Malard 1904)
Distribution. From the British Isles south to Spain. In Danish waters recorded from the northern Kattegat (Jensen & Knudsen 1995).

Kellia suborbicularis (Montagu 1803)
Distribution. S and W Iceland, the Faeroes, Norway off the Lofoten islands and south to the Mediterranean. In Danish waters recorded from the northern Kattegat and Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Intertidal to 120 m deep in crevices, shells or in borings made by other species (Poppe & Goto 1993).

Potidoma dorkiae (Clark 1852)
This species has been recorded only in a single find by Jensen & Knudsen (1995), and there are no subfossil finds from the literature, so it will not be considered further.

Astarte sulcata (da Costa 1778)
Distribution. SE and W Greenland, S and W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean. The species extends from the North Sea into the Kattegat, but is not common (Jensen & Spärck 1934).
Habitat. Sublittorally from 20 m and deeper on sand, mud and gravel bottoms.

Tridonta borealis Schumacher 1817
Distribution. This species is found in all regions of the north Atlantic except the British Isles (Madsen 1949). However, according to Petersen (1968) the species has not been recorded from the Faeroes. In the Danish waters the species extends from the deeper part of the northern North Sea (single finds) into the Kattegat, including the Øresund and the Baelt Sea, becoming very common in the Baltic (Jensen & Spärck 1934).
Occurrence. The Arctic, Subarctic and Boreal regions. Habitat. From below the tidal zone down to 250 m on mud, sand and gravel bottoms. The species is "a common member of all the zones of the Arctic Macoma community, and the Gomphina fluctuosa community" (Ockelmann 1958, p. 83).
Subfossil finds. The Baelt Sea and Limfjord regions, Holocene. Recorded from the Vendsyssel region both in the Early/Middle Weichselian (not in the Skaerumhede sequence) and the Late Weichselian (the Older Yoldia Sea and the Younger Yoldia Sea respectively).

Tridonta elliptica (Brown 1827)
Distribution. This species is found in all regions of the north Atlantic, including the British Isles (Madsen 1949). Petersen (1968) specified the occurrence of this species to be in the Clyde Sea and off the Isle of Man only. In the Danish waters it occurs in the Kattegat, Øresund, the Baelt Sea and the Baltic, where it becomes as common as T. borealis (Jensen & Spärck 1934).
Occurrence. The Arctic, Subarctic and Boreal regions. Considering the occurrences on the west coast of Britain it is also in the northern part of the Lusitanian region, but here probably mostly in deeper water.
Habitat. The vertical range for this species is off Iceland 6 to 300 m (Madsen 1949), and off the East Greenland coast it is most often taken between about 5 and 50 m, being abundant locally within the Arctic Macoma community (Ockelmann 1958).
Subfossil finds. Recorded from the North Sea during the Eemian, and in Vendsyssel during the Early/Middle Weichselian, being part of the Older Yoldia Sea found in the Skaerumhede sequence (Jessen et al. 1910).

Tridonta montagui (Dillwyn 1817)
Distribution. E and W Greenland, around Iceland, Spitsbergen, the Faeroes, Norway form north of Lofoten, and south to the Clyde Sea and Isle of Man (Petersen 1968), also recorded from the Bay of Biscay. It is present in the north western part of the North Sea (Petersen 1977) and common in the Kattegat, Øresund and extending into the Baelt Sea (Jensen & Spärck 1934).
Habitat. The vertical range off Iceland is 7-150 m (Madsen 1949) and in the North Sea sampled at depths between 40 and 75 m on mixed bottom in the trenches around the Dogger Bank (Petersen 1977, p. 226).
Subfossil finds. Recorded from the North Sea region during the Eemian and from the Vendsyssel area during the Early/Middle Weichselian (the Older Yoldia Sea). Fig. 67 Distribution. S and W Iceland, Norway north of Lofoten, and south to the Mediterranean (Madsen 1949). In Danish waters the species extends from the North Sea (Petersen 1977) into the Skagerrak, Limfjord, and Kattegat regions and the Øresund (Jensen & Spärck 1934).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 4 to 350 m deep on mud, sand and gravel bottoms (Poppe & Goto 1993).
Subfossil finds. The Kattegat, Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. From the Skagen Well recorded from the Subboreal and Subatlantic. There are Eemian records from the Baelt Sea, Kattegat, North Sea and Vendsyssel regions.

Parvicardium exiguum (Gmelin 1791)
Distribution. Norway north of Lofoten and south to the Mediterranean (Madsen 1949). In Danish waters common in bays and fjords, including the Limfjord. Considering all the variations belonging to the same species it extends into the Baelt Sea (Petersen 1888).
Occurrence. The Boreal and Lusitanian regions. Habitat. In general occurring from low tide to about 55 m deep (Poppe & Goto 1993);however, according to Rasmussen (1973) the species has its main occurrence along the shores and is associated with vegetation.
Subfossil finds. The Baelt Sea, Baltic, Kattegat, Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded also from the Baelt Sea, Kattegat, and North Sea regions during the Eemian.

Parvicardium hauniense (Petersen & Russell 1971)
Distribution. This newly established species has been recorded from recent Danish waters, but no subfossil records are at hand.

Parvicardium ovale (Sowerby 1840)
Distribution. Around Iceland, Norway north of Lofoten, and south to the Mediterranean (Madsen 1949). In Danish waters the species is found in all the regions except the Baltic extending only to Darss (Jensen & Spärck 1934).
Habitat. According to the Icelandic records (Madsen 1949) found between 5 to 350 m on bottoms such as mud, sand, clay and shell gravel with stones.
Subfossil finds. The Baelt Sea, Limfjord, North Sea and Vendsyssel regions, Holocene. From the North Sea and Vendsyssel regions also recorded from the Eemian.

Parvicardium scabrum (Philippi 1844)
Distribution. From Norway north of the Lofoten islands, and south to the Mediterranean (Madsen 1949). In Danish waters common in the Limfjord (Jensen & Spärck 1934) and recorded from the Kattegat, but questioned, as there may be two separate species (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone to several hundred metres deep on sand, mud and gravel bottoms (Poppe & Goto 1993). Occurrence. The Lusitanian region.
Habitat. From 1 to 60 m deep on rough sand and gravel bottoms.
Only subfossil finds. Recorded from the Eemian in the North Sea region. Fig. 68 Distribution. S and W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean at greater depths. In Danish waters common in the deeper part of the Skagerrak extending into the Kattegat, including the Øresund (Petersen 1888). The occurrence in the Limfjord is questioned (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 4 to 161 m on mud, sand and gravel bottoms (Poppe & Goto 1993). However, according to Madsen (1949) the species has around Iceland only been found at depths of more than 75 m, and the bottoms are recorded as sand with shells and stones or as ooze and clay. In Danish waters the species prefers

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone down to 60 m in clean sand.
Subfossil finds. The Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. From the Skagen Well recorded from the Subatlantic. During the Eemian recorded from the Baelt Sea region.

Lutraria lutraria (Linnaeus 1758)
Distribution. Norway off the Lofoten islands and south to the Mediterranean. Since 1990 live specimens have been taken in Danish waters near Frederikshavn and at the Skagerrak coast (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Intertidal down to 100 m, lives at depths up to 35 cm, burrowing in sand, sand-mud or gravel bottoms (Poppe & Goto 1993).

Spisula elliptica (Brown 1827)
Distribution. Around Iceland, the Faeroes, Norway north of Lofoten, and south to the English Channel and Gibraltar. The species occurs in the North Sea, extending into the Limfjord and Kattegat and the Øresund (Jensen & Knudsen 1995).
Habitat. Between 20 and 200 m deep in mud, sand and gravel bottoms.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone down to 100 m on sandy bottoms. In the North Sea found at 15-40 m depths in coarse sand (Petersen 1977).
Subfossil finds. The Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the Kattegat during the Eemian. Fig. 70a, b Distribution. Norway north of the Lofoten islands, and south to the Mediterranean (Petersen 1968). In Danish waters the species extends from the North Sea into the Kattegat, where it is also common. The species has been recorded both from the Øresund and the Baelt Sea (Jensen & Spärck 1934).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the Intertidal zone down to 200 m deep

Solecurtus chamasolen (da Costa 1778)
Distribution. Norway off the Lofoten islands, and south to the Mediterranean. In the Danish waters shells have been found near Frederikshavn (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 5 to 400 m deep on muddy bottoms.

Solecurtus scopula (Turton 1822)
Distribution. From the British Isles and south to the Mediterranean. Shells recorded from the northern Kattegat (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Mainly offshore to 110 m deep in muddy sand and on clean gravel bottoms (Poppe & Goto 1993).

Ensis americanus Gould 1870
Distribution. At present occurring down to the Øresund. However, the species has recently accidentally been transported to western Europe from the east coast of North America (Jensen & Knudsen 1995), so it will not be further considered.

Ensis arcuatus (Jeffreys 1865)
Distribution. The Faeroes, the British Isles and south to Spain. In Danish waters shells have been recorded from the Kattegat region, including the Øresund.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone to 40 m deep in sand and gravel bottoms.

Arcopagia crassa (Pennant 1778)
Distribution. From Norway south to West Africa. Only one record from Danish waters other than empty shells (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone down to 150 m deep in sand, mud and shell gravel bottoms (Poppe & Goto 1993).

Tellina donacina Linnaeus 1758
Distribution. From the Shetlands over the British Isles and south into the Mediterranean (Poppe & Goto 1993). The species occurs in the southern North Sea and has been recorded off Edinburgh (Jensen & Spärck 1934).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the low-tide mark to 200 m deep in sand, mud and gravel bottoms.
Only subfossil finds. Recorded from the North Sea during the Eemian.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone to depths of 100 m. In the North Sea found at depths of 30-50 m on hard bottoms (Petersen 1977).
Subfossil finds. From the Skagen Well recorded from the Subatlantic.

Gastrana fragilis (Linnaeus 1758)
Distribution. From the British Isles including the Shetlands, and south to the Mediterranean.

Occurrence. Mainly the Lusitanian region.
Habitat. From below the tidal zone to a depth of 750 m in sand, mud and gravel bottoms (Poppe & Goto 1993).
Subfossil finds. Recorded from the Baelt Sea, Kattegat and the North Sea during the Eemian.

Macoma balthica (Linnaeus 1758)
Distribution. W Greenland, Norway from north of Lofoten, and south to the British Isles (Petersen 1968) and Spain (Poppe & Goto 1993). The species is found in all the regions and extends far into the Baltic, but it is not common in the North Sea region from Blåvandshuk and north to Skagen (Jensen & Spärck 1934).
Habitat. This is a shallow-water species, but in the Baltic occurs also at depths of more than 50 m on soft bottoms (Muus 1967, p. 163). The species is also the characterising animal of the Petersen Macoma balthica community so often found in the inner Danish waters. However, Muus (op. cit., discussed the problem concerning this community in further detail and concluded that Petersen's community can be considered a serviceable way of giving a brief description of a faunal region for other marine biologists.
Subfossil finds. The Baelt Sea, Baltic, Kattegat, Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the Baelt Sea, Baltic, and the North Sea during the Eemian, and from the Vendsyssel area during the Late Weichselian.
Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. From the intertidal zone down to several hundred metres in the southern part of the distribution area. The species is the characteristic animal of the Arctic Macoma community (Thorson 1957).
Subfossil finds. From the Vendsyssel region, Holocene. Recorded from the Baltic and the Vendsyssel regions during the Eemian, from the Kattegat and Vendsyssel regions during the Early/Middle Weichselian (the Older Yoldia Sea stage), and finally from the Vendsyssel region also during the Late Weichselian (the Younger Yoldia Sea stage).

Macoma torelli (Steenstrup) Jensen 1904
Distribution. E and W Greenland and Spitsbergen. According to Ockelmann (1958) this species is regarded as having a high-Arctic main distribution and being restricted to the N Atlantic sector.

Occurrence. The Arctic region.
Habitat. Recorded rarely from Greenland sublittorally out to 90 m deep on clay and gravel (Ockelmann 1958).
Subfossil finds. Recorded from the Vendsyssel region during the Late Weichselian (the Younger Yoldia Sea).

Macoma loveni (Steenstrup) Jensen 1904
Distribution. W and E Greenland and Spitsbergen. According to Ockelmann (1958), the main distribution is high-Arctic with low-Arctic outposts.

Occurrence. The Arctic and Subarctic regions.
Habitat. At East Greenland the vertical range of the species has been recorded from 4-5 m to 207 m, and the species has been taken from various types of bottoms: clay, mud, sand, gravel and stony ones (Ockelmann 1958).
Subfossil finds. The Vendsyssel region during the Late Weichselian (the Younger Yoldia Sea). Fig. 75 Distribution. Norway off the Lofoten islands, and south to the Mediterranean (Madsen 1949). This species is found on the southern part of the Dogger Bank and along the west coast of Jylland (Petersen 1977) but not in the inner Danish waters (Jensen & Spärck 1934).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone down to 20 m in clean sand. One of the few molluscan species well suited to live in the coastal zone of sandy beaches.
Subfossil finds. The Limfjord on old beach ridges facing the Skagerrak (Petersen 1976), North Sea, Vendsyssel and Skagen regions, Holocene. From the Skagen Well recorded from the Subatlantic. Found in the North Sea during the Eemian.

Gari depressa (Pennant 1777)
Distribution. Norway off the Lofoten islands, and south to the Mediterranean.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone down to about 50 m in sand, mud and gravel bottoms.

Gari tellinella (Lamarck 1818)
Distribution. S and W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean. The species has been taken from the northern Kattegat (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone to a depth of 460 m in coarse sand, gravel and stone bottoms.

Scrobicularia plana (da Costa 1778)
Distribution. Norway off the Lofoten islands, and south to the Mediterranean (Madsen 1949). The species extends into the Baelt Sea at Kiel and Warnemünde (Jensen & Spärck 1934), and is also recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone to about 30 m in clay or muddy bottoms, often in estuaries (Poppe & Goto 1993). Jensen & Knudsen (1995) point to the occurrences in the Wadden Sea and to the sensitivity to severe winters, living in such shallow-water environments.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the infralittoral zone to a depth of 65 m in sand, mud or muddy gravel (Poppe & Goto 1993

Abra segmentum (Récluz 1843)
Distribution. From the west coast of France into the Mediterranean.

Occurrence. The Lusitanian region.
Habitat. In the infralittoral zone in sandy mud (Poppe & Goto 1993). It seems to be connected with the shallow-water environment, also with brackish water (Jensen & Spärck 1934).
Only subfossil finds. Recorded from the Baelt Sea and the North Sea during the Eemian. Fig. 80 Distribution. Around Iceland, the Faeroes, Norway north of Lofoten, and south to the Bay of Biscay. In the Danish waters, including the Limfjord, the species extends from the North Sea and Skagerrak as far as the Baltic (to Bornholm) (Jensen & Spärck 1934).

Arctica islandica (Linnaeus 1767)
Occurrence. The Subarctic, Boreal and (Lusitanian) regions. However, the species tends to live more deeply in the southern part of its range (Poppe & Goto 1993).
Habitat. Intertidal to 482 m in mud, sand or gravel bottoms. In the North Sea mainly from depths deeper than 40 m and from mixed bottoms (Petersen 1977). In inner Danish waters often at depths from 10-15 to 50-60 on clay or clayey bottoms (Jensen & Spärck 1934). According to Badarsson (1920), fishermen say that the species occurs in very shallow water, just below the low-water mark, in winter living deeply burrowed in the substrate, but in the summer often lying in abundance on the bottom.
Subfossil finds. The Kattegat, Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. From the Skagen Well recorded in the Subatlantic. In the Baelt Sea, Baltic and North Sea (there are (single find) records from the Eemian and the Vendsyssel region during the Late Weichselian (the Younger Yoldia Sea). Fig. 81 Distribution. From Norway off the Lofoten islands, and south to the Mediterranean. From Danish waters recorded from the Skagerrak. According to Jensen & Spärck (1934), very common in the deeper part of the Skagerrak. Jensen & Knudsen (1995) mentioned a single finding from the southern Kattegat.

Glossus humanus (Linnaeus 1758)
Distribution. S and W Iceland, Norway off the Lofoten islands, and south to the Mediterranean. In Danish waters recorded from the North Sea and Kattegat, where shells are common (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Offshore beyond 7 m on bottoms of sand, sandy mud or soft mud (Tebble 1966).
Subfossil finds. None. Fig. 82 Distribution. The Faeroes, Norway north of Lofoten, and south to the Mediterranean (Madsen 1949). In Danish waters the species extends from the North Sea, Limfjord and Skagerrak into the Kattegat and Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the infralittoral zone to 55 m deep on sand and mud bottoms (Poppe & Goto 1993). In the North Sea mainly from 20 to 40 m on sand to mixed bottoms (Petersen 1977). In the Skagerrak at depths of more than 100 m, but in the Kattegat at depths of less than 50 m, since the sand bottom is not to be found at deeper levels (Jensen & Spärck 1934).
Subfossil finds. The Limfjord, North Sea, Vendsyssel and Skagen areas, Holocene. From the Skagen Well recorded from the Subboreal and Subatlantic. During the Eemian recorded from the Baelt Sea, North Sea and Vendsyssel regions.

Clausinella fasciata (da Costa 1778)
Distribution. The Faeroes, Norway off the Lofoten islands, and south to the Mediterranean. From the North Sea the species extends into the Kattegat (Petersen 1888).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 4 to 110 m deep in sand, mud and gravel bottoms (Poppe & Goto 1993). In the North Sea in hard sand (Petersen 1977), and in the Kattegat in gravel and sand between 15 and 30 m (Petersen 1888, p. 143).

Paphia aurea (Gmelin 1791)
Distribution. Norway off the Lofoten islands, and south to the Mediterranean. The finds closest to Danish waters are from southern Norway (Jensen & Spärck 1934).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone down to 36 m deep in sand, mud and gravel bottoms.
Only subfossil finds. The Baelt Sea, Kattegat, Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the Kattegat region during the Eemian.

Paphia aurea senescens (Cocconi 1873)
Distribution. The only one of our Quaternary molluscs which does not live at present. Also found in Quaternary deposits in Italy (Jensen & Spärck 1934). Regarded as a Lusitanian species according to Nordmann (1913). However, Poppe & Goto (1993) regard the fossil valves found, for example along the coast of the Netherlands and Belgium, as a subspecies in which the differences from extant ones are minimal, and they propose that the relationship between the fossil and recent shells be restudied. From Nordmann (1913) and Cerulli-Irelli (1908) it seems right that Tapes senescens Doederl. and Tapes aureus var. eemiensis are identical. But as the relationship between T. senescens and T. aureus sensu stricto at the time of Nordmann (1913) was not clear, the position as a not extant subspecies given by Poppe and Goto is followed here.
Only subfossil finds. The Baelt Sea, Kattegat, and North Sea regions during the Eemian.

Tapes decussatus (Linnaeus 1758)
Distribution. Norway off the Lofoten islands, and south to the Mediterranean. Closest to Danish waters the species occurs off western Norway (Jensen & Spärck 1934).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the tidal zone to a depth of few metres in sand or muddy-gravel bottoms.
Only subfossil finds. The Kattegat, Limfjord, North Sea and Vendsyssel regions, Holocene. Recorded from the North Sea region during the Eemian. Fig. 83a, b Distribution. S and W Iceland, the Faeroes, Norway north of Lofoten, and south to the Mediterranean (Madsen 1949). In Danish waters the species extends from the North Sea into the Kattegat and Øresund (Jensen & Knudsen 1995), but has not been recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. At depths between 4 and 200 m on all types of bottoms (Poppe & Goto 1993). In the North Sea usually deeper than 50 m and on soft bottoms (Petersen 1977).
Subfossil finds. The Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. In the Skagen Well recorded from the Subatlantic. During the Eemian found in the Baelt Sea, Kattegat and North Sea regions.

Venerupis rhomboides (Pennant 1777)
Distribution. The Faeroes, Norway off the Lofoten islands (Madsen (1949) does not mention any Norwegian occurrence), and south to the Mediterranean (Petersen 1968). One pair of united valves recorded from the northern Kattegat (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone to 180 m deep (Poppe & Goto 1993) in gravel and mud bottoms.

Venerupis pullastra (Montagu 1803)
Distribution. Norway from north of the Lofoten islands, and south to the Mediterranean (Madsen 1949). From Danish waters recorded from the Limfjord and Katte-

Mya arenaria Linnaeus 1758
Distribution. Norway from north of the Lofoten islands, south to the British Isles (Petersen 1968). The species extends from the North Sea into the Limfjord and the inner Danish waters, including the Baltic (Jensen & Spärck 1934). It is a late immigrant, known from Europe in the Plio-Pleistocene (Strauch 1972, pp. 135-137) having been transferred from North America by man, presumably the Vikings, and dated back to the 13th century, i.e. well before Columbus (Petersen et al. 1992b).
Occurrence. Mainly in the Boreal region, but with new finds further to the south on the east coast of North America (Rasmussen & Heard 1994).
Habitat. From the tidal zone down to 6-7 m deep in sandy bottoms, the species avoids high-energy coastal environments (Jensen & Spärck 1934).
Subfossil finds. The records from the Baelt Sea and Vendsyssel might be of recent dates; only the occurrences at Jerup halfway up to the Skagen Spit have been dated and included in the Skagen area from the Subatlantic.

Mya truncata Linnaeus 1758
Distribution. W and E Greenland, Spitsbergen, around Iceland, the Faeroes, Norway from north of Lofoten, and south to the Bay of Biscay (Madsen 1949;Poppe & Goto 1993). The species extends from the North Sea into the Limfjord and the inner Danish waters as far as the Baelt Sea (Kiel and Warnemünde) (Jensen & Spärck 1934).
Occurrence. The Arctic, Subarctic, Boreal and Lusitanian regions.  Distribution. W and E Greenland, Spitsbergen, around Iceland, the Faeroes, Norway from north of Lofoten, and south to the Mediterranean (Madsen 1949). Following Jensen & Spärck (1934) who regard the records of Hiatella as one species, it is widely spread but not always common in all the Danish waters, it extends to Kiel in the Baelt Sea.
Habitat. "From the intertidal zone down to almost 1400 m fixed by its byssus on or in all kinds of substrate on all types of bottoms. Also found in holes previously bored by other species" (Poppe & Goto 1993, p. 130). However, Petersen (1977 states: "Both the systematics and nomenclature are insufficiently investigated for this genus". So with regard to the subfossil finds, the questions on species are even more difficult, as seen from Petersen (1986b, figs 2, 3), where forms with different habitat such as Hiatella cf. byssifera are found fixed on a stone taken as a grab sample in Kejser Franz Josephs Fjord, East Greenland, and as traces of Hiatella arctica in the Saxicava Sand of Late Weichselian age in Vendsyssel. However, here Símonarson et al. (1998) is followed, relating the more widely used and less specific name Hiatella arctica.
Subfossil finds. The Baelt Sea, Limfjord, North Sea, Vendsyssel and Skagen areas, Holocene. From the Skagen Well records from the Subboreal and Subatlantic. From the Eemian recorded from the Kattegat, North Sea, Vendsyssel and Skagen regions. In the Kattegat and Vendsyssel regions finds from the Early/Middle Weich-selian (the Older Yoldia Sea) and in the Vendsyssel region from the Late Weichselian (the Younger Yoldia Sea).

Hiatella rugosa (Linnaeus 1758)
Distribution. Jensen & Knudsen (1995) include this as a separate species and take it as part of the recent Danish shell-bearing fauna. Records from the literature on subfossil finds are therefore considered here. According to Poppe & Goto (1993), found from Norway south to the Mediterranean. Ockelmann (1958, p. 135 ff.), discussing the Hiatella taxonomy at some length, concludes that reservations must be made as to future separations of the Hiatella forms (H. arctica incl. of H. gallicana and H. pholadis) occurring in the northern hemisphere into valid species.
Subfossil finds. The Kattegat and Vendsyssel regions, Holocene. Fig. 86 Distribution. Norway off the Lofoten islands, and south to the Mediterranean (Madsen 1949). The species extends into the Kattegat and Øresund, although rare (Jensen & Knudsen 1995). It has been recorded from the Limfjord (Petersen 1986a).

Occurrence. The Boreal and Lusitanian regions.
Habitat. Offshore between 7 and 240 m deep in sand, mud or gravel bottoms (Poppe & Goto 1993). In the  Subfossil finds. The Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. In the Skagen Well recorded from the Subatlantic. During the Eemian recorded from the North Sea region.

Panomya arctica (Lamarck 1818)
Distribution. S and W Iceland, Norway from north of Lofoten, and south to the British Isles and Denmark (Madsen 1949). However, Petersen (1968) refers to empty shells from N Iceland and occurrences in the Clyde Sea and off the Isle of Man. In Danish waters only once taken alive near Skagen, otherwise shells only, but found as far south as Øresund (Jensen & Knudsen 1995).
Habitat. From the intertidal zone down to 300 m buried in mud or sand (Poppe & Goto 1993).
Subfossil finds. None. Fig. 87 Distribution. Norway off the Lofoten islands, and south to the Mediterranean (Madsen 1949). In the Danish waters, including the Limfjord, the species extends into the Baelt Sea as far as Kiel (Jensen & Spärck 1934).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the low intertidal zone to about 30 m deep, the species bores in semi-hard substrates such as clay (Poppe & Goto 1993).
Subfossil finds. The Baelt Sea, Limfjord, North Sea, Vendsyssel and Skagen regions, Holocene. From the Skagen Well recorded from the Subatlantic. During the Eemian found in the Baelt Sea and North Sea regions. Fig. 88a, b Distribution. Norway off the Lofoten islands, and south to the Mediterranean (Madsen 1949). In Danish waters only found to Frederikshavn and the Limfjord (Petersen 1986a; Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone to a depth of 10 m boring in different substrates, preferring clay bottoms (Poppe & Goto 1993).
Subfossil finds. The Limfjord, Vendsyssel and Skagen regions, Holocene. From the Skagen Well recorded from the Subatlantic.

Zirfaea crispata (Linnaeus 1758)
Distribution. Around Iceland, Norway from north of the Lofoten islands, and south to the Bay of Biscay (Madsen 1949). In the Danish waters, including the Limfjord, extending into the Baelt Sea as far as Kiel (Jensen & Spärck 1934).
Occurrence. Mainly Boreal with outposts into the Lusitanian region.
Habitat. From the low tide line to about 7 m deep, boring in semi-hard substrates (Poppe & Goto 1993). In the Danish waters the species has a wide extension, depending on the bottom substrates (Jensen & Spärck 1934): In the North Sea and Skagerrak peat and chalk; in the Limfjord cementstone, Mo-clay, chalk, peat and clay; and the Baelt Sea clayey bottoms.
Subfossil finds. The Baelt Sea, Limfjord, North Sea and Vendsyssel regions, Holocene. From the Baelt Sea region recorded from the Eemian and from the Vendsyssel region during the Late Weichselian (the Younger Yoldia Sea).

Lyonsia norwegica (Gmelin 1791)
Distribution. S and W Iceland, the Faeroes, Norway off the Lofoten islands, and south to the Mediterranean. In Danish waters recorded from the Kattegat.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 to 250 m deep in sand, silty sand and mud bottoms.
Subfossil finds. Recorded from the Skagen region, Holocene. In the Skagen Well recorded from the Preboreal and Boreal.

Lyonsia arenosa (Möller 1842)
Distribution. W and E Greenland, Spitsbergen, and Norway north of the Lofoten islands. Main distribution in the Arctic and Subarctic regions.

Habitat. From 3 to about 200 m on mixed bottoms (Ockelmann 1958).
Subfossil finds. Recorded from the Vendsyssel region during the Early/Middle Weichselian and the Late Weichselian (the Older Yoldia Sea and the Younger Yoldia Sea respectively). Fig. 89a, b Distribution. S and W Iceland, the Faeroes, Norway off the Lofoten islands, and south to Gibraltar (Petersen 1968). The species is rare in Danish waters and has only once been taken live in the Kattegat (Jensen & Spärck 1934), although shells are found in the Øresund (Jensen & Knudsen 1995).

Occurrence. The Boreal and Lusitanian regions.
Habitat. From the intertidal zone down to 110 m in sand, mud and gravel bottoms.
Subfossil finds. The North Sea and Skagen regions, Holocene. From the Skagen Well recorded from the Subatlantic. During the Eemian recorded from the Skagen region.

Occurrence. The Boreal and Lusitanian zones.
Habitat. Offshore down to over 800 m in mud and sand bottoms (Poppe & Goto 1993). In the Danish waters taken between 30-80 m (Jensen & Spärck 1934).
Subfossil finds. None. Fig. 90 Distribution. S and W Iceland, Norway off the Lofoten islands, and south to the Mediterranean (Madsen 1949). The species extends from the North Sea (Petersen 1977) into the Kattegat and Øresund, although with few records (Jensen & Knudsen 1995), and it has been re-

Thracia villosiuscula (MacGillivray 1827)
Distribution. S and W Iceland, the Faeroes, Norway off the Lofoten islands, and south to the British Isles (Petersen 1968). According to Poppe & Goto (1993) also found in the Mediterranean.

Occurrence. The Boreal and Lusitanian regions.
Habitat. In the North Sea sampled at depths between 20 and 50 m on hard sand (Petersen 1977).
Subfossil finds. Recorded from the North Sea region during the Eemian.

Occurrence. The Boreal and Lusitanian regions.
Habitat. From 20 m to 250 m deep in muddy sand and gravel bottoms (Poppe & Goto 1993). In Danish waters at depths between 30 and 60 m (Jensen & Spärck 1934).

Cuspidaria obesa (Lovén 1846)
Distribution. E and W Greenland, Spitsbergen, around Iceland, Norway north of the Lofoten islands, and south to the Mediterranean; however, to the south only at depths greater than 400 m (Madsen 1949). In Danish waters recorded from the Skagerrak and Kattegat. Occurrence. The Arctic, Subarctic and Boreal regions.
Habitat. At depths from 40 to 2500 m according to Madsen (1949), but in Danish waters fairly common in the deeper part of the Skagerrak.