150 PALEONTOLOGY OF CALIFORNIA. 



same form as the left ; is perhaps a little more convex, and wants 

 entirely the posterior umbonal ridge, the surface being rounded 

 instead of angular. Surface unknown. 



Figure 238, a left valve, natural size. The right valve is too imperfect for illus 

 tration. 



A cast of a single left valve and a broken right valve, from near Fort Tejon. 

 Collected by Dr. Horn. 



C. PARILIS, n. 8. 

 PL 29, Fig. 239, and 239 a. 



SHELL nearly equivalve, small, somewhat inequilateral; beaks 

 prominent, broad, strongly incurved, and inclined slightly for 

 ward. Anterior end sloping downwards abruptly, and regularly 

 rounded below ; posterior obliquely truncated and biangular ; a 

 distinct umbonal ridge passes from the beaks to the posterior 

 angle in both valves, most acute on the left. Basal margin of the 

 right valve regularly and broadly convex, straighter on the left. 

 Surface marked by prominent, concentric ribs, crossed by fine, 

 radiating lines. 



Figures, about twice natural size. 



Localities: Martinez to Marsh's, east of Mount Diablo ; and at San Diego (Divi 

 sion B.). 



ANATINA, Lam. 

 A. TRYONIANA, n. s. 



PL 29, Fig. 240. 



SHELL thin, compressed, long, narrow, and nearly equilateral, 

 twice as long as wide ; beaks central ; cardinal margin concave, 

 and slightly sloping in advance, nearly straight behind ; anterior 

 extremity rounded above, sloping convexly inwards below; pos 

 terior end narrow and regularly convex ; basal margin broadly 

 and regularly rounded. Surface polished 'and marked by fine, 

 concentric lines. 



