INTRODUCTION 7 



deeps, follow the isotherms and appear in depths of a few 

 fathoms in the north. 



There is a special fauna existing on the shallow i^lateau of 

 northeastern Bering Sea, which does not approach the shores. 

 This, though profuse in individuals, includes hardly any char- 

 acteristic species of bivalves and so does not enter into con- 

 siderations based on the present checklist. In a checklist of 

 gastropods it would furnish an amazing series of carnivorous 

 species, chiefly belonging to the Buccinidre, and including many 

 unique or peculiar forms never found al)out the shores. 



The present list contains about 474 species and varieties, 

 of vsdiich some 86 have never appeared in any previous enumera- 

 tion of the fauna, most of them ha^•ing been ver\' recently 

 described. Doubtless manv additions remain to l)e made with 

 future exploration. The known range of many of the species 

 will certainly be considerabl_y enlarged. 



The proper position of a few groups in the classification 

 remains to be elucidated, such as the Vesicomyacidae, Turtonia, 

 the Philobr3ddjE, Cooperella and a few others ; they are here 

 tentatively placed where the prevalent opinion indicates. 



T am under obligations to the U. S. National Museum, and 

 a multitude of Pacific Coast collectors for material and facilities 

 used in preparing this checklist. 



Species attributed to me with the date of iyi(). are on the 

 point of publication in the Proceedings of the U. S. National 

 Museum. 



- WILLIAM HEALEY DALE 



