]8 PALEONTOLOGY OF CALIFORNIA. 



ZIRPH^EA, Leach. 



Z. DENTATA, n. 8. 

 PL 3, Fig. 81, 31 a. 



SHELL large, subcyliudrical, thin ; ends broadly gaping ; beaka 

 anterior to the middle ; covered by the dorsal plate ; posterior 

 dorsal margin of valves thin and sharply reflexed. Surface of 

 anterior third of shell marked by serrated, squamose plates, as 

 In Z. crispata; a faint line or rib passes between the middle and 

 posterior third of the width, from the beaks obliquely down to 

 the base; dorsal plate heavy, compressed, and divided into two 

 concave surfaces by a sharp, angular ridge, commencing at the 

 posterior end, and running forwards, slightly curved, ending in 

 a tooth at a point about a third of the length of the plate from 

 the anterior extremity. 



Figures, natural size ; fig. 31 a, represents the dorsal plate. 



Locality: A single specimen from the Pliocene beds at the east end of Kirker's 

 Pass, Contra Costa County. 



This shell is closely allied to Z. crispata ; but differs in its more regularly cylin 

 drical form, the marked reflection of the posterior dorsal margin, and the angular 

 dentated dorsal plate. 



PANDORA, Brug. 



P. SCAPHA, n. 8. 

 PL 4, Fig. 32. 



SHELL small, irregularly subquadrate; right valve flat; left 

 valve slightly convex; beaks small, about a third of the width 

 from the anterior end, which is prominent and regularly convex; 

 cardinal margin slightly concave near the beaks, straight behind ; 

 base broadly and regularly curved; posterior end narrow and 

 prominent. Surface marked by a few lines of growth. 



Figure, magnified about a third. 



