northern portion of them, and mostly increasing in abundance of individuals as they approach towards the Arctic circle: such are,
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Astarte borealis.
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Fusus barvicensis.
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Leda pygmæa (fossil in the newer pliocene deposits of Italy, Germany, and Britain, but taken alive and abundantly, by Mr. MacAndrew, who dredged it in 1845, in the sound of Sleye, where it is associated with boreal forms) belongs to this assemblage. It is identical with Nucula lenticula of Möller, from Greenland.
4th. Of species now known, living only in European seas, north of Britain, or in the seas of Greenland and Boreal America, as
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Astarte compressa, var. multi-
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Terebratula psittacea.
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5. Of species not now known existing, and unknown fossil in previous deposits.
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Fusus allied to F. crispus.
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Nassa monensis.
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6. Of species, fossil in the coralline or red crag, but still existing in the South-European though not in the British Seas.
Turritella incrassata.
7. Of extinct species, fossil also in the crag.
Tornatella pyramidata.
This fauna, then, is composed of living British species of northern origin, some of which are now confined to climates far colder than our own, with a few forms supposed to be extinct, and one or two shells of southern origin, or known only in the crag. It is important to observe that the latter are from the southernmost parts of these deposits in Ireland, where are also found members of the crag monstrosity of Fusus antiquus, known as Fusus contrarius, and the variety of Purpura lapillus,
