476 University of California Publications in Geology [Vol. 8 



strongly arcuate ; posterior end bluntly pointed ; anterior end broadly 

 and evenly rounded. Surface of valves marked by medium fine in- 

 cremental lines. Right valve slightly flexed near the posterior ex- 

 tremity; bordering the posterior dorsal edge is a narrow depressed 

 area on which is a faint groove extending from the posterior extremity 

 about half way to the beaks ; this depressed area is separated from the 

 remainder of the surface by a raised line or ridge. Left valve with 

 an obscure, narrow, posterior depressed area on which there is usually 

 a faint groove corresponding to the groove seen on the depressed area 

 of the right valve. Shell near the posterior end slightly twisted to the 

 right. Ligamental groove rather long, about half the length of pos- 

 terior dorsal edge. Of the two cardinal teeth in right valve, the pos- 

 terior cardinal is the larger and is bifid; in the left valve the anterior 

 cardinal is the larger and is bifid. 



Dimensions. — Type specimen: length, 13 mm.; height, 13 mm.; 

 diameter of both valves, 8 mm. 



Occurrence. — This species is found at several localities in the Upper 

 San Pablo Group on the south side of Mount Diablo and in the type 

 section on San Pablo Bay ; also on Rocky Ridge and Las Trampas 

 Ridge, University of California localities 1671, 767 and 400. 



SANGUINOLARIA ALATA Gabb 



Plate 61, figure 14; rjlate 62, figure 5 



Gari alata Gabb. Palaeontology of California, vol. 2, p. 21, pi. 5, fig. 36, 

 1869. 



Shell oval, equivalved, inequilateral, compressed; beaks inconspic- 

 uous; nymph plates very prominent; beaks slightly anterior to the 

 middle of the shell. Anterior dorsal edge straight ; anterior end evenly 

 rounded ; posterior dorsal edge longer than anterior and slightly con- 

 cave and straight ; base evenly and gently arcuate ; posterior end evenly 

 rounded. A very strong nymph plate on each valve extending over 

 two-thirds the length of the posterior dorsal edge with a marked longi- 

 tudinal groove on each, running along their entire length. Two car- 

 dinal teeth in each valve, anterior cardinals more prominent than 

 posterior ; ' anterior cardinal of left valve bifid, posterior cardinal 

 elongate, not so high and slanting obliquely toward the rear; anterior 

 cardinal of right valve not bifid, posterior cardinal elongate and bifid. 

 W. H. Dall (Transactions of the Wagner Free Institute of Science, 

 vol. 3, pt. 5, p. 974), in referring to this species says: "The super- 



