1916] 



Dickerson: Tejon Eocene of California 485 



ventral margin broadly arcuate ; posterior end subtruncate, resembling 

 that of Marcia quadrata (Gabb) ; anterior end moderately convex; 

 posterior dorsal margin slightly convex with gentle slope ; anterior 

 dorsal margin slightly convex with moderate slope to the rounded 

 anterior end. 



This species somewhat resembles Marcia quadrata (Gabb) but is 

 less elongate, its anterior end is more rounded and its posterior dorsal 

 slope is greater. 



Named in honor of T. A. Conrad, the eminent palaeontologist who 

 first recognized Eocene strata on the Pacific Coast. 



Dimensions. — Length, 18 mm. ; height, 15 mm. ; thickness, 5 mm. 



Occurrence. — The type was found at University of California 

 Locality 1817, lower Tejon, northwest of Coalinga, California. 



PHACOIDES (MYRTEA) TAFFANA, n. sp. 

 Plate 36, figure 11 



Shell small, compact, trigonal ; beak small, prominent, opisthodetic ; 

 concentric growth lines prominent, lamelliform. A marked posterior 

 fold extends from the beak to the posterior end ; posterior dorsal 

 margin slightly convex ; anterior dorsal margin slightly concave ; 

 base rounded. Area small and not distinctly set off. Pallial line 

 simple, entire ; two cardinal teeth in right valve, the posterior one 

 being bifid ; two cardinal teeth in left valve ; a posterior lateral and 

 an anterior lateral tooth are found in the right valve witli correspond- 

 ing sockets in the left valve. 



Named in honor of Mr. J. A. Taff, Geologist, Southern Pacific 

 Company. 



This species is easily distinguished from Diplodonta polita 

 (Gabb) by its lamelliform concentric ribs. 



Dimensions. — Height of a right valve, 5 mm. ; length, 5.5 mm. 

 Occurrence. — University of California Locality 672. 



SPISULA MBRRIAMI Packard 

 Plate 39, figures 2a, 2b, 2c 

 Shell small, trigonal, equivalve, nearly equilateral, slightly ven- 

 tricose, ornamented by numerous fine concentric ridges which are more 

 pronounced and less numerous on the anterior and posterior dorsal 

 areas than upon the other portions of the shell ; beaks moderately 

 prominent, anterior dorsal area limited by a distinct ridge extending 

 from the umbo to the anterior extremity ; the margin of this area is 



