2 BULLETIN 112, UNITED STATES NATIONAL MUSEUM. 



Atlantic and Pacific; the Temperate into Aleutian, Oregonian, and 

 Californian; the Tropic into Gulf of California!!, Panamic, and 

 Ecuadorian. These divisions coincide with differences of tempera- 

 ture of the sea water, generally indicated by the distribution of 

 ocean currents. 



Taking the distribution of a single family these distinctions might 

 have their boundaries somewhat modified, but on the average of the 

 whole molluscan fauna they appear to be well established. 



The limits of these faunas are not in all cases sharply defined. 

 Some of the less sensitive species will be found to range far beyond 

 the divisional boundaries. In southeastern Alaska, Avhere the in- 

 shore channels of the Alexander Archipelago are kept cold by the 

 drainage from glacier streams, many Arctic forms persist; perhaps 

 relicts from the glacial period; while on the outer fringe of the 

 islands quite a number of the more southern species extend their 

 range northward in the warmer ocean waters. 



The student of this list will notice many more species, which from 

 southern California extend their range to Panama or even Peru, than 

 are recorded in any .previous publication. 



There is a special faunula existing on the shallow plateau of 

 northeastern Bering Sea. It is composed largely of carnivorous 

 gastropods, which do not approach the shores. This has furnished 

 a multitude of Buccinidae to the present summary, and was, before 

 the incursion of the whaling fleet, the summer feeding ground of 

 vast numbers of the Pacific walrus. 



Before concluding this introduction it would be improper to omit 

 a few words of gratitude to the numerous private students and col- 

 lectors whose investigations and contributions to the collection have 

 added a multitude of new forms to the known fauna, and to whom a 

 large part of such completeness as this summary may possess is 

 necessarily due. Detailed acknowledgments must await another 

 occasion, but the evidence of their activities is on permanent record 

 in the collections of the United States National Museum, and will 

 afford to future students an indispensable basis for study. 



Acknowledgment must also be made to the Director of the United 

 States Geological Survey for the opportunity afforded me to work 

 upon and publish the (present paper. 



In indicating a figure illustrative of the species standard works, 

 such as are generally accessible in large libraries, have been chosen 

 when possible. If the figure in the work referred to bears there a 

 different specific designation from the one here adopted, it may be 

 understood that the former name is a synonym of the one used in this 

 summary, or for some other reason is not accepted. 



Every effort to keep the classification adopted as up to date as 

 possible has been made; though this is a subject on which differences 



