136 CALIFORNIA ACADEMY OP SCIENCES. 



This species is distinguishable from T. biaecta by its much smaller size, more 

 central umbones and less prominent lunule. Dr. Dall says that 2\ gouldi has been 

 mistaken for Cryptodon flexuosus by West Coast collectors. 



Rather common in the Pleistocene of Dead Man Island and Timm's Point. 

 Not found above the horizon in the San Pedro deposits, so far as known. 



Living. — Catalina Island (Cooper): Catalina Island, ten fathoms (Arnold). 



Pleistocene. — Santa Barbara (Cooper). 



Pliocene. — Santa Barbara; San Diego well (Cooper): San Pedro (Arnold). 



Superfamily LEPTONACEA. 



Family XXIV. LEPTONID^. 



Genus Bornia I'hiUjrpl. 



Shell ovate or subtrigonal, subequilateral, with a more or less flattened disk; the peri- 

 ostracum usually brilliant; the surface smooth or divaricately more or less plicate; pallial line not 

 sinuated, and the pallial area piquantly punctate or radially striate; hinge with one moderately long 

 posterior, and two shorter anterior, lamina- in the left valve; in the right, one anterior and one 

 longer, sometimes remote, posterior lamina; one or both of the anterior laminae in either valve may 

 have the aspect of cardinals; hinge-plate usually excavated. 



Ty2:)e, Bornia corhuloides (Phil.). 



67. Bornia retifera Dull. 



Plate XVII, Fig. 12. 



Bornia retifera Dall, Proc. U. S. Nat. Mus., Vol. XXI, 1899, p. 889, PI. LXXXVII, fig. 2. 



Shell thin, white, moderately conve.x, rounded, trigonal, nearly equilateral; beaks distinct, 

 not high; surface polished, with faint incremental lines and minute, close punctations whose inter- 

 spaces give the effect of a fine netting ; hinge narrow, delicate; one tooth opposite beak, then a 

 depression posterior to this, and then a second tooth completely filling the anterior end of the 

 posterior ligamental groove; adductor scars rounded and high up. 



Dimensio7is — Long. 7 mm.; alt. 5.5 mm.; diam. 3 mm. 



Looks like a Kellla laperou»ii, but is distinguishable by the microscopic 

 sculpture and hinge. Specimens identified by Dr. Dall. 



One right valve from the lower San Pedro series of Deadman Island, which is 

 figured herewith, and is now in the collection of Delos Arnold. 



Living. — Station 2,900, thirteen fathoms, off Santa Barbara (Dall). 



Pleistocene. — San Pedro (Arnold). 



Genus Kellia Turton. 



Section Kellia Turtou a. s. 



Shell rounded and inflated, concentrically striated or smooth ; with an obsolete external 

 ligament and a large internal resilium without a lithodesma ; two anterior and two posterior teeth in 



