1914] Dickerson: Fauna of the Martinez Eocene of Calif ornia 133 



Dimensions. — Length, 23 mm. ; height, 18 mm. ; convexity, 4 mm. 



Occurrence. — Common at University of California Locality 340, 

 Martinez Group southwest of Mount Diablo. 



The sculpture resembles that of P. acutilineatus (Conrad) but its 

 height is proportionally much less than that of P. acutilineatus. Its 

 long lunule and escutcheon are also distinctive features. 



Named for its occurrence near Mount Diablo. 



DOSINIA( ?) LAWSONI, n. sp. 

 Plate 10, figure 9 



Shell, medium in size, subglobular, very convex, with full rounded 

 beaks centrally placed; anterior dorsal margin excavated under beaks, 

 where a small lunule is found ; posterior dorsal margin nearly straight, 

 with steep slope to the rounded posterior end; anterior end narrowly 

 rounded ; ventral margin arcuate ; surface smooth or marked by fine 

 incremental lines only. 



Dimensions. — Length, 16 mm. ; height, 14 mm. ; convexity, 4.5 mm. 



Occurrence. — University of California localities 243 and 340, Mar- 

 tinez limestone southwest of Mount Diablo. 



The type is a small specimen used on account of its fair preserva- 

 tion. The species is far more convex than the other Eocene species of 

 this genus. In this respect it resembles D. inflata Gabb of the Chieo, 

 but the shape and position of the beaks is entirely different. 



Named in honor of Professor A. C. Lawson, University of Cali- 

 fornia. 



VENUS (?), sp. 

 Plate 10, figure 10 



Shell thick subtriangular, convex; beaks very high, nearly central; 

 posterior dorsal margin gently convex, sloping steeply to the rounded 

 posterior; anterior margin very concave and abrupt; ventral margin 

 rounded ; lunule indistinct. 



Dimensions. — Length, 26 mm. ; height, 28 mm. ; convexity, 7 mm. 



Occurrence. — University of California localities 790, vicinity of 

 Lower Lake, and 340, southwest of Mount Diablo. 



The specimen is a cast, hence the generic reference is doubtful. It 

 differs from V. lenticularis Gabb of the Chieo in that the beak is 

 considerably higher and the posterior dorsal margin is decidedly 



