148 University of California Publications in Geology [Vol.11 



hind the ligamental groove slopes down more abruptly to the posterior 

 end ; one of the big differences between the two species is the larger 

 angle between the pallial line and the pallial sinus on P. lorenzana, 

 the apex of the sinus pointing just a little below the beaks while on 

 P. dalli it points to about the middle of the anterior muscle scar. 



PIT ARIA? sp. 

 Plate 14, figure 8 



Several poorly preserved specimens of a species which appears to 

 belong to the genus Pitaria, were found at University of California 

 locality 76 at the base of the Kirker formation. The outline of this 

 form, as shown on plate 14, figure 8, differs considerably from that 

 of P. lorenzana, found in the San Ramon formation in the vicinity 

 of "Walnut Creek ; also, the angle between the pallial sinus and the 

 pallial line is less than on this latter species ; the concentric sculptur- 

 ing appears to be more lamellate, but this last character may be 

 due to difference in weathering of the specimens from the different 

 localities. 



Genus CALLOCARDIA Adams 

 CALLOCAEDIA (AGRIOPOMA) CALIFORNICA, n. sp. 

 Plate 11, figures 2, 3, 4 and 11 

 Type specimen 11107, Coll. Invert. Palae. Univ. Calif., loe. 1131 



Shell thin, medium in size, broadly ovate and rather strongly ventricose. Beaks 

 fairly prominent, prosogyrous, strongly inturned, situated about three-fourths the 

 distance from the posterior to the anterior end. Anterior end rather strongly 

 produced, subacutely rounded; posterior end broadly subtruncate. Surface smooth 

 except for medium fine, somewhat irregular incremental lines; posteriorly the 

 surface is very strongly depressed, being slightly flattened along the dorsal 

 margin, with the ligament tending to be immersed below the flattened area. 

 Lunule fairly large, lanceolate, marked off by an impressed line; dorsal margin 

 of lunular area strongly pouting. In the left valve the cardinals are thin and 

 entire, the posterior one being the longest and situated close up to the feeble 

 nymph plate; anterior lateral also thin, pyramidal, not situated on a well-defined 

 platform. Posterior cardinal of right valve long, fairly heavy and grooved; the 

 other two cardinals are entire. Adductor scars indistinct; pallial sinus short and 

 rather acutely rounded. Ligamental groove deep and strongly immersed. 



Dimensions. — Type specimen: length, 49 mm.; height, 31 mm.; height, meas- 

 ured just posterior to the beaks, 34 mm. ; diameter of both valves, 29 mm. 



Occurrence. — University of California locality 1131. 



The specimens referred to this species were all sent to Dr. W. H. 

 Dall for generic determination ; he states that it belongs to the genus 

 Callocardia, subgenus Agriopoma. According to Dall, this group 

 heretofore has been known only from eastern America and Japan in 

 the Recent state. 



