172 PALAEONTOLOGY OF CALIFORNIA. 



C. Remondianum, n. 8. 



PL 23, Fig. 153. 



Shell small, subcordate, inequilateral, wider than long; oeaks 

 central, large, prominent, slightly inclined forward, with the sides 

 sloping rapidly towards both ends; anterior end broadly and 

 regularly convex; posterior end abruptly truncated; basal margin 

 rounded, most prominent posteriorly ; a rounded angle passes 

 from the beaks to the posterior basal angle ; in advance of this, 

 the surface is prominently convex ; behind it, it is flattened and 

 descends abruptly to the posterior margin. Surface marked by 

 about forty square, radiating ribs, with flat interspaces ; these 

 ribs are very large on the umbonal angle, and decrease gradually 

 in size in front and behind, until they are mere lines. Internal 

 edge crenulated. 



Figure, about three times natural size. 



Localities: From near Benicia, Division A.; also at "Wright's Gulch," near 

 Shasta City ; collected by Mr. Remond. 



C. Cooperii, 11. S. 

 PL 24, Fig. 154, and 154 a. 



Shell broad, cordate, equilateral ; beaks small, central, promi- 

 nent ; cardinal margins sloping, rounded, not very abruptly, on 

 both sides ; ends symmetrical ; base regularly convex. Surface 

 marked by a large number of minute, rounded, radiating ribs; 

 these ribs are a little larger on the posterior face of the shell, but 

 the surface so covered is not separated from the rest by any angle 

 or carina. 



Figures, natural size. 



Localities: From Division B., at Martinez; San Diego; also near Canada de 

 las Uvas. 



Closely related to C. multiradiatum, nob., of Alabama and (?) New Jersey; but 

 distinguished by the broader outline, and the difference in size of the ribs on the 

 posterior face, from those on the rest of the surface. 



