TERTIARY FOSSILS. 23 



equal in size ; margin minutely creimlated ; the purple color be 

 tween the pallial line and the base is very persistent. 



Figure, natural size. 



Locality : From the Post-Pliocene beds on the beach at Santa Barbara. 



Allied to V. (Mercenaria) Ducatelli, Conrad, of the New Jersey Miocene, but 

 much broader posteriorly, and the ribs are more numerous than are represented 

 in the figure of that species. 



CHIONE, Megerle. 

 C. MATHEWSONII, n. s. 



PI. 5, Fig. 39. 



SHELL very thick, obliquely cordate, very inequilateral ; beaks 

 anterior; anterior end sinuous ; base broadly rounded ; posterior 

 end prominent, narrow. Lunule lanceolate, impressed. Surface 

 marked by numerous irregular, concentric ribs; adjoining the 

 cardinal edge and posterior to the beaks, is a narrow flat space 

 running almost to the posterior end of the shell ; inner margin 

 entire, not crenulated. Pallial sinus deep; lower side curved, 

 upper side straight. 



Figure, natural size. 



Locality and position : Not rare in the Miocene, south of Martinez; collected by 

 Mr. Mathewson and Dr. Fish. 



This shell is quite variable in outline, though all of the other characters are 

 very constant. It seems related to C. succincta = Nuttallii and Californica, but 

 differs in the entire absence of radiating ribs. 



C. WHITNEYI, n. s. 



PI. 6, Fig. 40. 



SHELL thin, oblique, rounded subcordate; beaks small, pro 

 duced, pointing forwards ; anterior end rounded, prominent, ex 

 cavated above; base regularly convex; posterior cardinal margin 

 rapidly descending, convex. Surface marked by numerous fine 



