Vol. VII] WARING— STRATIGRAPHIC AND FAUNAL RELATIONS 63 



dinal margin, with which it makes a sharp smooth curve; 

 umbone small and depressed; surface ornamented by large 

 concentric lines of growth. Locality 2, L. S. J. U. Pal. Coll. 



Mactra gabbiana Anderson 

 PI. 8, Fig. 11 



M. gabbiana Anderson, Proc. Cal. Acad., 3rd Series, vol. 

 2, No. l,p. 74, pi. 7, fig. 156, 1902. 



Shell thick, deeply sculptured by evenly spaced concentric 

 lines. Posterior cardinal margin straight; anterior cardinal 

 margin excavated ; basal margin broadly curved ; extremities 

 sharply curved. Beaks depressed and turned forward. Lo- 

 cality 3, L. S. J. U. Pal. Coll. 



Pecten (Propeamusium) cowperi, new species 

 PI. 7, Figs. 1 and 2 



This species is easily recognized as being closely allied to 

 Gabb's Pecten interradiatus of the Eocene. The shell is 

 small, subcircular, equivalve, equilateral, compressed, thin; 

 upper valve, ears equal, moderately large; lower (right) valve, 

 right ear long, deeply and narrowly emarginate; right valve 

 with about nine large internal ribs, equally spaced, which are 

 rounded and extend from the umbone nearly to the margin 

 where they are abruptly truncated ; external surface orna- 

 mented with many fine equally spaced concentric lines ; upper 

 valve with four to eight rather large rounded internal riblets 

 which extend from the umbone nearly to margins ; external 

 surface marked by many fine radial ribs which are nearly ob- 

 solete near the anterior and posterior of the shell. Locality 

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



This species has also been found by the writer in the Chico 

 shales of the Tesla sheet. Probably the unnamed Pecten* 

 allied to P. interradiatus from "Road cutting below Prof. 

 Richer's house at mouth of Strawberry Canyon, Berkeley. 



• U. S. Geol. Surv. Prof. Paper No. 47, p. 54. 



