Vol. 4 1 Weaver. — Palaeontology of the Martinez Group. 115 



Dimensions: — The maximum length is 30 mm. and the great- 

 est width 15 mm. 



Occurrence : — This form has been found about three miles 

 southwest of the town of Martinez, associated with Lima multi- 

 radiata. It also occurs about three miles south of Martinez, on 

 the east side of the road leading to Walnut Creek. It is charac- 

 teristic of both the upper and the lower Martinez beds. 



Area biloba, n. sp. 



Pl. 12, Fig. 4. 



The shell is strongly arched, moderately inflated and ine- 

 quilateral. The beaks are small, incurved and grooved. From 

 the interspace between the two heads of the beak there runs a 

 moderately deep groove over the surface of the shell toward the 

 base. The beak is located about one-third the distance from the 

 anterior end. The anterior end is somewhat narrow. The pos- 

 terior end is obliquely truncated. The base is broadly rounded. 

 Behind the umbonal ridge the surface is nearly flat. The sur- 

 face is marked by numerous ribs, and these are crossed by many 

 regular lines of growth. 



Dimensions : — The maximum length of the specimen described 

 is 9.5 mm., and the greatest width 3.5 mm. 



Occurrence: — This shell has been found about three miles 

 southwest of Martinez, in association with Lima niidtiradiata, 

 and also about five miles southwest, near the head of Vaca Canon. 

 It occurs in both the upper and lower beds. 



Tellina martinezensis, n. sp. 



Pl. 12, Fig. 3. 



The shell is small, thin, compressed, and about twice as long 

 as the distance from the beak to the base. The anterior end is 

 rather broad. The posterior end is considerably narrower and 

 truncated obliquely. The beaks are small and nearly central. 

 The basal margin is convex. A ridge, especially well marked 

 near the beak but gradually becoming fainter toward the base, 

 passes from the beak to the posterior basal angle. The surface 

 is ornamented by numerous small, regular, concentric lines. 



