296 University of California Publications in Geology [Vol. 9 



Anterior lateral low, long ; posterior lateral also rather low. Hinge 

 of right valve unknown. The dimensions of the type are: height, 

 55 mm., length, 53 mm., convexity, 17 mm. 



This is the largest of the known West Coast Eocene species. It 

 is characterized . by its pronounced posterior ridge, its escutcheon 

 and its small heavy cardinal. It differs from S. merriami, which 

 it superficially resembles, in its more massive cardinal, more promi- 

 nent posterior ridge and in the lack of pronounced ribs. 



The type was obtained from University of California Locality 

 463. The following is the description given by R. E. Dickerson: 

 "SE % of NW 14 of Sec, 32, T 10 N, R 20 W. On a branch 

 canon of Salt Creek, 150 feet above the bottom. Mount Pinos sheet, 

 California." 



Occurrence. — Eocene : Tejon series. 



SPISULA BREVIROSTRATA, n. sp. 

 Plate 28, figures la, lb and 2 

 Shell medium-sized, compressed, equilateral, umbones small, adja- 

 cent; anterior dorsal edge sloping in a nearly straight line to the 

 rather attenuated anterior extremity. A fairly distinct ridge, 

 extending from the umbones to the anterior extremity, limits a 

 depressed area on the anterior margin of the shell ; posterior dorsal 

 edge very slightly convex, sloping regularly to the broadly rounded 

 extremity ; base arcuate. Hinge plate relatively wide ; chondophore 

 very shallow, triangular in shape, probably overhung by a small 

 spur; left cardinal large, not overhanging the resilifer, situated ven- 

 trally on the hinge plate ; arms of equal length, their ventral edges 

 rounded ; laterals high, short ; anterior one round-topped and shorter 

 than the posterior one, which is acutely pointed ; dorsal base of the 

 anterior lateral is close to, but slightly dorsal to, the anterior arm 

 of the cardinal. Pallial line distant, pallial sinus reaching nearly 

 to the middle of the shell. Hinge of the right valve unknown. The 

 dimensions of the type are : length, 78 mm., height, 60 mm., con- 

 vexity, 15 mm. 



This species has been confused with S. falcata, from which it 

 differs in being relatively higher and in possessing a large left car- 

 dinal the arms of which are of equal length. 



The type of this species was collected by Bruce Martin at Uni- 

 versity of California Locality 1875. Martin described this station 



