1914] Dickerson: Fauna of the Martinez Eocene of California 123 



Rhynchonella. Its ventral valve is marked by concentric growth lines 

 and by microscopic radiating lines. A very prominent median fold 

 extends from the center of the shell to its edge. Cardinal slopes 

 gentle, straight. The outer portion of the shell appears to have been 

 removed. 



Dimensions. Length, 9 mm. ; height, 8 mm. ; convexity, 3 mm. 



Occurrence. Martinez near Lower Lake. 



PELECYPODA 



LEDA PACKARDI, n. sp. 

 Plate 7, figures 3a, 35 



Shell thin, marked by fine rounded concentric lines, short, convex ; 

 beaks central, small but prominent; anterior dorsal margin, slightly 

 sloping; posterior, straight; anterior end rounded; posterior end 

 bluntly pointed with apex of point at end of straight posterior dorsal 

 margin; base rounded from anterior to middle of posterior ventral 

 margin; from this point the slightly curving posterior margin slopes 

 abruptly upward to the posterior extremity. This species differs from 

 all the other California ledas in shape and in the central position of 

 its beaks. The oddly blunted rostrum is another distinguishing feature. 



Dimensions. Length of medium-sized specimen, 10 mm. ; height, 

 5 mm. ; convexity, 3 mm. 



Occurrence. University of California Locality 784; Meretrix dalli 

 zone north of Mount Diablo and the Trochocyathus zitteli zone of the 

 Martinez type section, near Muir Station. 



Named in honor of Mr. Earl Packard, who assisted the writer in 

 collecting Martinez fossils in Lake County. 



LEDA MILLERI, n. sp. 

 Plate 7, figure 4 



Shell small, moderately convex; beak, prominent, located one-third 

 of the distance from anterior end. Posterior dorsal edge straight with 

 a very slight slope to a blunt pointed posterior end. Anterior dorsal 

 edge straight with a slightly greater slope than posterior dorsal edge. 

 Ventral margin gently convex. This margin curves sharply toward 

 the two pointed extremities of the shell. 



Dimensions. Length, 9 mm. ; height, 5 mm. ; convexity, 2 mm. 



Occurrence. University of California Locality 1556. 



Named in honor of Dr. L. H. Miller. 



