The MoUusca of the Arctic Coast of America collected by 

 the Canadian Arctic Expedition west from Bathurst 

 Inlet with an Appended Report on a Collection 

 of Pleistocene Fossil MoUusca. 



By William Healey Dall, A.M., D.Sc, LL.D. 



Honorary Curator of MoUusks, U. S. Nat. Museum. 



(With three plates.) 



The collection of MoUusca in the region indicated by the title of this report 

 is of special interest, since the only collections hitherto made between the 

 Mackenzie delta and the archipelago to the eastward were due to R. Macfarlane 

 of the Hudson's Bay Company, factor of the most northern post of the company, 

 and who, about 1863, made a journey from the head of the delta to the sea and 

 collected Ghrysodomus heros, Astarte borealis, ai^d very thin valves of Mytilus 

 edulis, in considerable numbers. The fauna to the eastward of the delta has 

 remained entirely unknown. The great outpour of fresh water from the 

 Mackenzie might reasonably have proved a barrier which the characteristic 

 species of the western Arctic ocean might not have been able to pass, and there 

 was, therefore, a possibility that "the eastward fauna would show a c6nsiderable 

 infusion of Greenlandic forms. 



It may be observed here that the Bering Strait region and the Polar sea 

 north of it have a fauna which, when the truly circumpolar species are eliminated, 

 is markedly distinct from that of the Greenlandic and boreal Atlantic seas. 

 During the Pliocene the Arctic land was lower, and there was more easy commu- 

 nication between the two areas, as is made evident by the discovery in each 

 Pliocene fauna of species now extinct there, but which have survived in the other 

 area. It is convenient, therefore, to refer to the respective faunas of the two 

 areas by the denomination Western or Eastern Arctic fauna. 



The result of the study of the collection was somewhat unexpected, since 

 it proved that out of all the species collected east of cape Bathurst only five can 

 lie considered at present as characteristically Eastern Arctic, namely : — 



Area glacidlis Gray. 

 Lamellidoris cf. liturata Beck. 

 Philine finmarchica M. Sars. 

 LameUaria gronlandica Moller. 

 Littorina gronlandica Morch. 



The fresh-water and land species are, with the exception of the Physa, 

 common to most of boreal America and have an entirely different distribution 

 from the marine forms. They include: — 



Succinea chrysis Wester lund. 

 Agriolimax hyperboreus Westerlund. 

 Physa jennessi, n. sp. 

 Aplexa hypnorum Linn^. 

 Lymnaea palustris vahli Beck. 

 Lymnaea siagnalis appressa Say. 

 Valvata lewisii Currier. 

 Pisidium rotundatum Prime. 



3 a 

 45508—1* 



