202 PALAEONTOLOGY OF CALIFORNIA. 



base regularly rounded; ears moderate; the right ear of the lower 

 valve long, narrow, and deeply emarginate; left ear obliquely 

 truncated. Surface marked by very fine, concentric lines. 



Figure, two and a half times the natural size. 



Locality : Cottonwood Creek, Shasta County (Division A.). 



This shell is allied to P. operculiformis, but is smaller, the lower valve is more 

 convex, there is a difference in outline, and the emarginated ear differs widely 

 from the corresponding one of that species. 



A small Pecten, of about the same size with the present, but sculptured like P. 

 Traskii, is found at Martinez. I have not ventured to name it. 



LIMA, Brug. 



(Ctenoides, Raduh, Klein.) 

 L. MICROTIS, n. s. 



PI. 26, Fig. 189. 



SHELL oblique, compressed ; anterior side prominent, forming 

 a subelliptical curve; posterior nearly straight; base rounded; 

 beaks small; anterior ear small, obliquely truncated; posterior 

 unknown, probably nearly obsolete ; surface nearly flat, with a 

 very gentle convexity, except near the posterior margin, where 

 it is abruptly bent down, forming a marked truncation; orna 

 mented by numerous flat, radiating, entire ribs, not dichotomous ; 

 the interspaces forming shallow grooves, serrated on the sides 

 and marked in the middle by series of small pits or punctations. 



Figure, natural size. 



Localities: Two specimens only have been found. The one figured is from Cot 

 tonwood Creek ; the other was associated with the specimen of Meretrix longa, ut 

 supra (Division A.). 



This shell resembles L. ovalis, Desh. (Plagiostoma ovalis, Sow. ) ; but is more 

 slender, the ribs are broader and flat, wider than the interspaces, and the inter 

 costal punctse are much smaller and more distant. 



