NORTHWEST COAST MARINE SJIELEBEARING MOLLUSKS. 3 



of opinion are to be expected. The International rules of nomencla- 

 ture have been rigidly followed, in the belief that the progress of 

 science depends largely on standardization of names, however pain- 

 ful it is to note the disappearance of familiar but erroneous designa- 

 tions. The accuracy called for by the present state of the science 

 should not be relaxed to satisfy the protests of amateurs in taxonomy. 

 In compiling this list I have taken advantage of the work of my 

 colleague, Dr. Paul Bartsch, who has with great care and intense 

 microscopical study worked out the species of minute forms, such as 

 the Pyramidellidae, Rissoidae, Synceratidae, and Caecidae, and have 

 adopted his results as published in the Proceedings of the United 

 States National Museum during the last few years, with only such 

 changes as the progress of science since their publication has made 

 advisable. Many forms which on a superficial examination by the 

 older authors were regarded as mere mutations of a single species 

 have proved on microscopic study to possess constant characters fully 

 entitling them to specific rank. In general, whenever the characters 

 seem to justify it, I have preferred to record separately forms which, 

 on the examination of only a few specimens, might have been 

 regarded as mere mutations. By thus separating them, often from 

 examination of a multitude of individuals, attention is called to their 

 characters, and future students will have an opportunity to exercise 

 their judgment on the question of specific distinction when otherwise 

 it might have been entirely overlooked. 



Many of the species with a wide geographical range follow the 

 isotherms, and when collected in the north appear to be denizens of 

 moderate depths, but in the southern part of their range are found 

 only at great depths where the temperature of the water is the same 

 as in their more boreal habitat. It becomes difficult therefore to de- 

 termine which species are really members of the archibenthal fauna. 

 I have in the following discussion regarded only those found exclu- 

 sively in depths of over 200 fathoms as belonging to that fauna, and 

 therefore the number of species of that group in the table may seem 

 unduly small, for many of the others also reach great depths in part 

 of their range. 



A very few excej)tional cases occur where spe :ies are known from 

 deep water in the northern part of their range yet have been obtained 

 in moderate depths in the south. Transpoitation and regurgitation 

 by fishes may account for this anomaly which must await more 

 thorough collection of living specimens for explanation. 



In certain cases of anomalous distribution reported by collectors, 

 and when I have not examined personally authentic specimens, I have 

 appended the name of the authority for the locality. A former hain't 

 of the Spanish women of southern California, of preparing shell 

 work for sale to tourists and of carrying their baskets of shells (often 



