MIOCENE PECTENS. 87 



Miocene (middle or lower Rohlar, 12 miles from Piiso Ro})les, and on ranch of 

 W. F. Cxillis, 10 miles southwest of Paso Robles, San Luis Obispo County (J. P. 

 Smith); Oil City, Fresno County (Eldridge). 



Pecten (Plagioctenittm) eldridgei n. sp. 



n. XXV, fiKS. 3, 3a, Sh, 4, 4a, 5, 5o, and 6. 



J)e.-<cription.—iihe\[ averaging about 20 millimeters in altitude, nearly as high 

 as long, equivalve, somewhat oblique (the posterior portion being the longer), very 

 thick ^nd heavy, very ventricose, and with serrate margins; base unequally 

 rounded; sides somewhat concave above and sloping at a moderately steep angle. 

 Right valve with 19 or 20 small, rather low but sharply defined, squarish ribs; 

 interspaces about one-half as wide as ribs, channeled, and with flat bottoms; 

 surface of disk ornamented by numerous sharp concentric lines which loop back 

 over the ribs; more or less prominent constrictions, indicating interrupted growth, 

 are common on most specimens; hinge line equal to about three-fourths length 

 of disk; anterior ear slightly longer than posterior, deeply notched, and orna- 

 mented l\y 3 or -1 prominent radiating ridges and numerous imbricating incre- 

 mental lines; posterior ear rectangularly truncated and ornamented by 8 or 10 

 radiating ridges and incremental sculpture. Left valve similar to right, except 

 that the" ribs are slightly narrower and more rounded; ears similar to those of 

 right valve except that the anterior one is not as deeply notched. Hinge similar 

 to" that of F. circular Is except stronger and with the auricular crura much more 

 highly developed. Adductor impressions very deep. 



I)/me»sions.—A\t. 20 mm.; long. 21 mm.; hinge line 1.5 mm.; diameter 15 mm. 



This species is similar in many respects to F. circularis, but is characterized 

 by its smaller size, greater ventricosity, thicker and heavier shell, deep adductor 

 impressions, and more or less prominent constrictions. It sometimes attains an 

 altitude of 4:5 millimeters, as shown by fragments collected at the type locality. 



/'. ,-ldrid(i>'i appears to be confined to the oil-liearing strata of the San 

 Joaquin Valley, which are probably San Pablo or upper Miocene in age. 



The type," which is figured and is now in the United States National Museum, 

 was collected in the hills south of the Dabney water wells, McKittrick district, Kern 

 County. Named in honor of the late Mr. G. H. Eldridge, of the United States 

 Geological Survey. 



RANGE. 



Miocene (upper). McKittrick district, Kern County (Eldridge): Buena Vista and 

 McKittrick, Kern County (Watts). 



Pecten (Plagioctenixim) neahensis n. sp. 



PI. XV, figs. 2, 2a and 2h. 



Description.— M\n\t»\iQ\\ averaging al)out 45 millimeters in altitude, somewhat 

 longer than high, subequivalve, subequilateral, prominently ventricose, especially 

 for^about the first 25 millimeters of altitude, after which it is sometimes more 

 compressed; sides concave aliove; base evenly rounded; margins smooth. Right 

 valve with 19 prominent rounded ribs, separated by somewhat narrower 



