Mr. II. M 'Andrew on the Distribution of Mollusca. 435 



the Arctic Sea, or vice versa, the deep-water species, like others, 

 are limited in their range, and characteristic of the region to 

 which they belong. I have myself dredged at depths reaching 

 to about 200 fathoms on the coast of Finmark, and invariably 

 obtained from the deepest water shells of a peculiarly northern 

 character — for example, Lima excavata, Pecten Grcenlandicus, 

 Leda limatula, and Chiton alveolus ; and Dr. Alph. Milne-Edwards, 

 in a paper " upon some Animals obtained at great Depths," 

 quoted from the 'Comptes Rendus/ in the 'Annals of Nat. 

 Hist/ for September last, mentions, as communicated to him 

 by M. Valenciennes, Voluta Junonia from 70 fathoms in the 

 Gulf of Mexico, and Lima excavata from 264 fathoms on the 

 coast of Greenland, and that, upon portions of a submarine 

 cable which had been recovered from a depth of 1000 to 1500 fa- 

 thoms between Cagliare and Bona, he had found Ostrea cochlear, 

 Pecten opercularis var. Audouini, Pecten Testce, Monodonta Urn- 

 bata, and Fusus lamellosus — all species previously known as in- 

 habitants of the Mediterranean Sea. 



It is an unquestioned fact that a considerable portion of the 

 species of Mollusca inhabiting any one zoological province may 

 be found in other provinces ; but it is not by a simple compa- 

 rison of the lists of species that we can determine the similarity 

 or divergence of the fauna of separate localities, as the difference 

 between them may consist in a few characteristic forms, which 

 may be especially developed in each. That one and the same 

 marine fauna does not extend from the Mediterranean coast 

 of Morocco to Finmark and Spitzbergen must be patent to the 

 most cursory observer. The former district contains numerous 

 genera peculiar to the warmer region of the earth, where many 

 of them are very widely distributed, including Conus, Cyprcea (as 

 distinguished from Trivia), Typhis, Marginella (as distinguished 

 from Erato), Triton, Ranella, Pisania, Fasciolaria, Dolium, Cassis, 

 Turbo, Cymba, Cancellaria (as distinguished from Admete), Mitra, 

 Fossarus, Columbella, Mesalia, Gadinia, Siphonaria, Haliotis, 

 Sigaretus, Crepidula, Argonauta, Vermetus, Siliquaria, Spondylus, 

 Chama, Cardita, besides a few supposed to be local, such as Cas- 

 sidaria, Lobiger, Pedicularia, Thecidia, &c, most of which, in the 

 Atlantic, are not to be found beyond the 40th, and none beyond 

 the 50th, parallel of latitude *. The fauna of the Arctic and 

 sub-Arctic regions, though by no means deficient in the number 

 of individuals, is distinguished from that of more southern lati- 

 tudes by the comparative fewness of its genera and species, 

 likewise by several peculiar genera, as Trichotropis, Admete, 



* One species of Mitra and one of Cardita inhabit the Arctic seas of 

 America. Manyelia nana and Holbbllii are related to Astyris(avara), Adams, 

 a subgenus of Columbella. Turritella lactea is not a Mesalia. 



28* 



