140 PALAEONTOLOGY OF CALIFORNIA. 



small, regular, rounded ribs, with sometimes finer ones interpo- 

 lated. 



Figure, slightly magnified. 



Locality: Northeast of Martinez; San Diego (Div. B.); and Gurry's, south of 

 Mount Diahlo (Div. A.). 



EMARGINULA, Lam. 



E. RADIATA, 11. S. 

 PL 21, Fig. 102, and 102 a. 



Shell subelliptical, moderately elevated ; apex a little in ad- 

 vance of the middle, slightly curved. Surface marked by about 

 eighteen rather large radiating ribs, with occasional small inter- 

 mediate ones; these are crossed by a few irregular, concentric 

 lines. Emargination narrow and rather deep ; the corresponding 

 ridge sharply defined and nearly square. 



Length, .3 inch; width, .18 inch; height, .12 inch. 



Locality : Texas Flat, Placer County. 



I have seen hut a single specimen of this rare and beautiful little shell. It is 

 in the collection of the California Academy of Natural Sciences. 



PATELLA, Linn. 

 P. Traskii, n. s. 



PL 21, Fig. 103. 



Shell depressed, subelliptical; apex subcentral; height vari- 

 able. Surface marked by from twelve to fourteen radiating ribs 

 with intermediate lines, from one to three in number ; these 

 are crossed by irregular lines of growth. Margin gently undu- 

 lated, the ends of the ribs being more prominent than the inter- 

 spaces. Muscular impression horseshoe-shaped; ends connected 

 by a sharp impressed line. 



Figures, natural size. 



Locality : Texas Flat, Placer County (Division A.j. 



