A ZOOGEOGKAPHTC STUDY BASED ON THE PYKA^IIDEL- 

 LTD ^lOLLUSKS OF THE WEST COAST OF AMERICA. 



By Paul Bartsch, 



uAssistant Curator, Diuision of Mollusks, United States National Museum. 



INTRODUCTION. 



In tills paper I have considered all the available data relating to 

 the distribution of tlio recent west American species of tliis family 

 described in Bulletin 68 of the United States National Museum 

 and the additional forms described in the supplemental paper pub- 

 lished in these Proceedings, volume 42, page 261, 1912. There have 

 also been included here notes on specimens from the west coast of 

 America, wliich have been determined for various institutions and 

 individuals since the publication of that monograph. The disposition 

 of tliis material is mentioned under each reference in the present 

 paper, and I may say here that I wish to extend grateful thanks to all 

 coiTespondents and institutions mentioned in Bulletin 68 and in the 

 supplemental paper, for it is almost entirely due to their cooperation 

 that the present study has been made possible. I wish also to 

 express my sincere appreciation and thanks to Dr. William H. Dall, 

 honorary curator of the Division of Mollusks, for lending a patient 

 ear to my troubles and giving kindly counsel during the years that 

 I have been at work upon this gi"oup. 



In the preparation of this manuscript a card was prepared for 

 each species, on wliich has been noted the number of specimens 

 examined, the locality from which they were obtained, dejith in 

 fathoms, bottom temperature, and disposition of material, the last 

 subdivided into two columns, one citing the catalogue number, 

 the other the collection in which the material occurs. It would have 

 beiMi desirable to add the salinity and the physiograpliic conditions 

 of each station, but unfortunately few data are available on these 

 points. I have noted them wherever they were to bo had. 



These specific cards fall readily into a series of zoogeogi-aphic divi- 

 sions, wliich in turn can be easily groujied to correspond with the 

 great provinces outlined by S. P. Woodward, Manual of Mollusca, 

 London, 1851-1856, pages 355 and 372 to 377, and later more fully 



Proceedings U. S. National Museum. Vol. 42— No. 1906. 



297 



