Geol.— Vol. II.] ANDERSON— ST RATIGRAPHIC STUDY 197 



Pectunculus septentrionalis Middendorf. 



Plate XVII, Figs. S6 and 87. 



Pcciunculus septentrionalis (Midd.) Carpenter, Brit. Assn. Rept. 1856, 



p. 219. 

 Glycymeris septentrionalis (Midd.) Arnold, Mem. Calif. Acad. Sci. v. 3, 



p. loi, pi. XVIII, fig. 10. 



This species is well described by Arnold, though the 

 sculpture of the shell is not shown in his figure. It will be 

 noticed upon a comparison of the figures that the form from 

 San Pedro has a smaller ligamental area and a somewhat 

 higher beak than the form here represented. 



Occurrence. — This species is abundant in the Etchegoin 

 Beds both north and south of Coalinga, and is identical with 

 or closely related to a similar species occurring in the San 

 Pablo Beds on San Pablo Bay, Contra Costa County. 



Diplodonta harfordi n. sp. 



Plate XVII, Figs. 88 and 89. 



Shell not large, rotund, sub-quadrate in outline; beaks nearly central, low, 

 closely approaching each other; cardinal margin straight, excavated; anterior 

 margin sometimes a little produced, but generally rounded; surface marked 

 only by concentric lines. 



This shell is allied to D. orbella Gould, but has a less 

 prominent beak and a straight hinge margin. 



Occurrence. — This shell occurs abundantly in the Coalinga 

 Beds west of Coalinjra. 



Pecten coalingaensis Arnold. 



Plate XVIII, Figs. 94-98. 



Pecten {Pecten) coalingaensis Arnold. 



Shell moderate in size, the largest having a diameter of ^}i inches; 

 inequivalve, radially ribbed; lower valve convex, upper concave. 



Arnold's description of this species is not yet published, 

 but as the specimens here figured are from his type locality 

 and have been identified by Dr. Arnold, there is no doubt 



