[From the Proceediugs of the California Academy of Soicnres, October 7, 1872. 



A partial comparison of the Conehology of portions of the At- 

 lantic and Pacific coasts of North America. 



BY ROBERT E. C. STEARNS. 



A striking feature in the Concliological fauna of that part of the Pacific 

 coast included in the Califoruian and Vancouver Zoological province wlien 

 compared with the molhiscan fauna of the Atlantic coast from the Arctic seas 

 to Georgia, is the preponderance in the former of those forms of mollusean life 

 which are embraced in the Order of Scutibranchiata* 



The Scutibranchiatc Gasteropods, or shield-gilled crawlers, comprise a great 

 number of raoUasks, all of which are marine, and which inhabit the sea shore 

 principally the littoral and laminarian zones, subsisting on marine vegetation ; 

 thus we find the beautiful group of Calllostoma upon the larger algaj as well 

 as the unique Trochiscus {T. Soiverhyt), and Chlorostoma crawling over the 

 sedimentary rocks, upon which grows the green Cladophora or some allied 

 vegetable form upon which it feeds, and which also is the favorite food of 

 several species of limpets. 



The Order of Scutibranchiata according to the Adams's, includes the families 

 of Nentidce (none of which are found in the Californian and Oregonian province, 

 though they begin to appear on the coast of Lower California); the Trochulce, 

 which is largely represented by the following genera: Eutropia one species; 

 Lepiothijm three species ; Pachypoma and Pomaulax one species each ; Liolia 

 one, perhaps two species ; ThaloHa and Trockbcus one species each ; Callios- 

 toma, Chlorostoma, Omphalius, Margarita and Gibbula each by several species. 



The Family of Haliotidce which is represented by several species all of large 

 size, widely distributed and exceedingly numerous in individuals ; Fissurella 

 including Lucapina, Glyphis and Clypidella, also Pundurella and Emarginula. 



DentaliadcE by two or more species ; Teduridm by several species of Acmcrn 

 also by Scurra ,■ Gadinia by one and Nacella by six or more species, 



Ckitonida by numerous species and great numbers of individuals. 



It may be that some of the groups included by the Messrs. Adams in the 

 Order referred to, as our knowledge increases, will require to be separated or 

 removed, but so far as the purposes of comparison as made herein are con- 

 sidered, the result will not be materially impaired. 



The total number of marine mollusean species and well marked varieties with- 

 in the Californian and Oregonian province, so far as known and determined, is 

 not far from 630, of which about 200 are Bivalves; and of the remaining 430, 123 



*Vide AdaniB* Genera of Recent Mollusca, Vol. I, p. 376. 



