64 THE NAUTILUS. 



are common to the southern part of Chile, the Magellanic region, 

 and the Falkland Islands. 



The largest species of the genus, which reaches 58 mm. long 

 and 28 mm. high, is P. major Ball, 1891, ranging from the 

 Pribiloff Islands, Bering Sea, to Boca de Quadra in southern 

 Alaska. It has faint transverse lines of callus but no pits, and 

 the shell is very thin for its size. Lastly P. galeata Gould, 

 1849, has strong pits and props, with a finely threaded, close- 

 set, radial sculpture. It ranges from Unalashka, Aleutian 

 Islands, to the Santa Barbara Islands, California. 



A NEW FORM OF BATHYTOMA FROM THE UPPER PLEISTOCENE OF BAN 



PEDRO, CAL. 



BY PROF. J. J. RIVERS. 



Plate III, figs. B, c, represent two examples selected from six 

 discovered by Dr. F. C. Clark, who has been for several years 

 an investigator of the coast species of both fossil and recent 

 Mollusca. 



Dr. Clark and myself have a partnership in Paleontology, 

 each holding equal rights under the firm name of "Rivers and 

 Clark". Dr. Clark does most of the excavating of strata, while 

 I have the delight to nominate the species when I am able. 

 Our material is great, and unless we can obtain assistance, years 

 will elapse before a complete catalogue will be forthcoming. 



Bathytoma clarkiana Rivers. I name this in honor of my 

 colleague, Dr. F. C. Clark of Santa Monica, Cal. The fossil is 

 heavily charged throughout the whole of its structure with car- 

 bonate of lime. The columella is thicker than in any described 

 species. If the shell be placed with its aperture downwards, 

 many conchologists would think it an exotic species of Mitra. 

 But there are none of the known species of Bathytoma that re- 

 presents this form in its attenuate outline. This figure will ex- 

 plain the oblique condition of the sutures that divide the whorls. 



