50 CALIFORNIA ACADEMY OF SCIENCES [Peoc. 4th Ser. 



the height, older individuals of this species tending to have 

 the height considerably greater than the length, thus differ- 

 ing from Cucullcua ponderosa Whiteaves.^^ Umbone broad, 

 curved slightly anteriorly, and deeply excavated both an- 

 teriorly and posteriorly; anterior margin broadly rounded, 

 basal margin nearly straight, posterior truncated ; posterior 

 umbonal angle sharp; anterior umbonal angle broadly 

 rounded; hinge area broad and long, extending about two- 

 thirds length of shell ; exterior of shell ornamented by fine 

 radial lines and fine irregular lines of growth, the lines of 

 growth obscuring the fine radial lines in older individuals. 



The species is probably closely related to CucullcBa mathew- 

 sonii Gabb, of the Martinez. It differs in having much finer 

 ribs and broader umbone. Locality 2, L. S. J. U. Pal. Coll. 

 Named for Mr. H. W. Young of Stanford University. 



Dosinia milthoidea, new species 

 PI. 8, Fig. 5 



Shell of medium thickness, circular and inflated ; beak 

 small, excavated anteriorly; cardinal margin convex, sloping 

 into the circular posterior margin ; anterior and basal margins 

 rounded ; surface ornamented by fine concentric lines of 

 growth and three or four irregularly spaced major concentric 

 lines. Locality 2, L. S. J. U. Pal. Col. 



Venus pertenuis Gabb 



Dosinia pertenuis Gabb, Pal. Cal., vol. 1, p. 167, pi. 30, fig. 

 253. 



Our specimens of this species are about the size of the one 

 Gabb figured. The shell is thin and subcircular; the anterior 

 and basal margins form a regular curve, while the cardinal 

 margin is slightly arched and joins the posterior margin 

 with a small angle; an inward truncation of the cardinal bor- 

 der runs from the beaks to the posterior angle; surface 

 marked by fine concentric lines of growth. Locality 3, L. S. 

 J. U. Pal. Coll. 



"Whiteaves, Geol. Surv. Canada, vol. 1, pt. 4, p. 294, pi. 38, figs. 1 and la. 



