DESCRIPTIONS OF NEW SPECIES OF MOLLUSCA FROM THE 

 NORTH PACIFIC OCEAN IN THE COLLECTION OF THE 

 UNITED STATES NATIONAL MUSEUM. 



By William Healey Dall, 



Honorary Curator of Mollasks, United States National Museum. 



INTRODUCTION. 



In preparing a census of the shell-bearing Marine Mollnsca of the 

 west coast of North America from the Arctic Sea to San Diego, 

 California, with the view of compiling a classified checklist of these 

 animals, it became necessary to review the entire fauna of the west 

 coast of both Americas, as it proved that the range of many species 

 is far greater than had hitherto been assumed. The National Col- 

 lection is probably the richest in the world for the region indicated, 

 including the dredgings of the United States Bureau of Fisheries 

 steamer Allatross, as well as the contributions of a multitude of 

 collectors during nearly half a century. The presence of the types of 

 species described by Gould, Carpenter, and Stearns among the earlier 

 collectors has facilitated the accurate determination of many more 

 or less obscure forms. Among the species examined, especially 

 those from warmer waters and from depths not reached by private 

 collectors, there were found many which seemed to be undescribed. 



In order to avoid the publication in the checklist of manuscript 

 names or the omission of species needed for completeness, it has 

 seemed best to prepare diagnoses of such forms as appear clearly 

 new. This has already been done in another publication for the 

 group of Chitons and for the family of Turritidae (foi-merly known as 

 the Pleurotomidae) and the latter difficult group fully illustrated. 

 It is hoped that the other unfigured species may be illustrated later, 

 but under present conditions the best that could be done was the 

 preparation of full and exact diagnoses and measurements. The 

 types of these new species are, with hardly an exception, preserved in 

 the National Collection. 



A thorough and exhaustive collection of the mollusca of the 

 Panamic fauna is still a desideratum and can hardly fail, when made, 

 to enormously increase the number of species known, especially 

 among the minute forms. There are particular areas like the Gulf 

 of Dulce in Central America and the St. Elena region on the north- 



Proceedings U. S. National Museum. Vol. 56— No. 2295. 



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