272 PROCEEDINGS OF THE CALIFORNIA 



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

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

 which are embraced in the Order of Scutibranchiata.* 



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

 number of mollusks, 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 Calliostoma upon the larger algte as well 

 as the unique Trochiscus [T. Sowerbyi), and G/ilorostoma 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 Neritida (none of which are found in the Califoruian and Oregonian province, 

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

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

 Leptothyra three species ; Paclii/poma and Pomaulax one species each ; Liotia 

 one, perhaps two species ; Tludotia and Troclnscus one species each ; Callios- 

 toma, CIdorostoma, Omphalius, Margarita and Gibhula each by several species. 



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

 size, widely distributed and exceedingly numerous in individuals ; Fissurella 

 mclniVmg Lucapina, Glyphis and Clypidella, also Puncturetla and Emargimda- 



Dentaliada by two or more species ; TeduridcE by several species of Acmma 

 also by Scurra ; Gadinia by one and Nacella by six or more species. 



Chitonidm 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 molluscan 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 

 are included within the Scutibranchs ; of this latter number about 40 belong to 

 the Chitonida? and the same number to the Trochida?. 



Of the 247 marine gasteropods enumerated by the late Dr. Stimpson in the 

 Smithsonian Institution Check-list, as found from the Arctic Seas to Georgia, 

 32 only, or less than one-eighth, come within the Order mentioned ; of this 

 comparatively small number seven (7) are Chitons and fourteen (14) belong to 

 the Trocliidcc, while Haliotisf is without a representative ; the Trochida: with- 

 in this province are not represented by such marked or unique characters as 

 distinguish their relatives on the West Coast. 



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



tA solitary specimen of Haliolis, of small size, was obtained through dredging in the 

 Gnlf Stream, foiu- or five years ago, by Count L. F. Ponrtalcs, of the U. S. Coast Survey, but 

 south of Georgia. / 



