THE NAUTILUS. 



VOL. XX. AUGUST, 19O6. No. 4. 



THE WEST AMERICAN SPECIES OF PLEUROTOMA, SUBGENUS GENOTA. 



BY WILLIAM JAMES RAYMOND. 



Five species of the subgenus Genota, section Dolichotoma, have 

 been described from the Pacific coast of North America. Three of 

 the species have been figured ; two have not hitherto. Specimens of 

 all five, including the types of four, being temporarily in possession 

 of the writer, it seemed desirable to bring them together in a single 

 photographic plate. Apparently derived from a common stock, and 

 arising in late tertiary time, the nominal species are closely allied. 

 Yet there is convenience in retaining the present specific designa- 

 tions of forms which are readily distinguishable. Two of the species 

 have not thus far been found living. As the deeper water along the 

 coast is explored, they may possibly be discovered in the dredge, 

 together with other forms not now known. 



Pleurotoma ( Genota) carpenleriana Gabb. 



Pleurotoma (Surcula) carpenteriana Gabb. Proc. Cal. Acad. Nat. 

 Sci., 1865, p. 183 ; Pal. Cal., vol. 2, p. 5, pi. 1, fig. 8. 



Pliocene San Fernando and Santa Rosa (Gabb) ; San Diego 

 (Ball). 



Pleistocene Santa Barbara and San Pedro (Gabb); San Pedro, 

 San Diego and Ventura (Arnold) ; Santa Monica (Rivers). 



Living Drake's Bay, 30 fathoms (Arnheim); Monterey to San 

 Diego (Cooper); San Pedro, Santa Catalina Island and San Diego, 

 10 to 100 fathoms (Raymond); Cerros Island (Dall). 



This is the largest and most plentiful species of the group. It is 



