462 University of California Publications in Geology [Vol. 8 



and the concentric lines of growth are more regular; the anterior 

 dorsal edge slopes down more obliquely from the beaks. 



Dimensions. — Height of type (pi. 49, fig. 1), 90 mm.; length, 92 

 mm. ; diameter of one valve, about 20 mm. Height of cotype (pi. 52, 

 fig. 1), 100 mm.; length, about 85 mm.; diameter, about 23 mm. 



Occurrence. — From the base of the San Pablo Group in the region 

 of Kirker Pass to the north of Mount Diablo. Here it is associated 

 with Pecten crassicardo, Spisula albaria and Spisula catilliformis, 

 Scutella gabbii, etc. ; University of California locality 100. Also from 

 the Lower San Pablo on San Pablo Bay, University of California 

 locality 1532. 



DOSINIA (DOSINELLA) MEREIAMI, var. OCCIDENTALIS, n. var. 

 Plate 50, figure 1 



This variety differs from D. merriami, n. sp., chiefly in outline; 

 the shell is higher in proportion to the length; the posterior dorsal 

 slope is steeper, being only slightly arcuate ; the ventral margin is 

 steeper; the anterior dorsal shoulder is less prominent; the beaks are 

 higher and narrower. The sculpturing is very much the same as on 

 D. merriami, n. sp., and it also has the depressed flattened area along 

 the posterior dorsal margin. The hinge plates of the two are prac- 

 tically alike. 



Dimensions. — Height, 88 mm. ; length, 73 mm. 



Occurrence. — D. merriami, var. occidentalis comes from a higher 

 horizon than D. merriami, n. sp. ; it is found on the south side of 

 Mount Diablo, University of California localities 481, 482, 1485, asso- 

 ciated with Astroclapsis whitneyi, Astroclapsis tumidus, Trophon 

 carisaensis. It is also very common in the Santa Margarita beds to the 

 north of Coalinga. 



TIVELA (PACHYDESMA) DIABLOENSIS, n. sp. 

 Plate 54, figures 5 and 6; plate 55, figure 1 

 Shell large, trigonal in outline, slightly inequilateral; beaks strongly 

 inturned. Posterior dorsal margin nearly straight to slightly con- 

 cave ; anterior dorsal margin straight ; ventral edge long and gently 

 arcuate ; posterior dorsal margin strongly depressed, with a fairly 

 distinct ridge or carina separating it from the remaining surface of 



