PLIOCENE PECTENS. 97 



PeCTEN (PeCTEX) COALIXdAEN.SIS II. sp. 



PI. IV, tigs. 4, 4a, and 5. 



Description. — Shell about -15 millimeters in altitude, longer than high, pliino- 

 convex, or nearly ,so, equilateral, and with smooth margins. Right valve 

 ventrieose and ornamented ))v about ^ly) rib.s whieh have narrow, somewhat eoiivex 

 top.s, and sides which slope at angle.s of about 45 ; interspaees quite deeply 

 impressed, channeled, and flat bottomed; surface sculptured by tine incremental 

 lines; hinge line slightly longer than one-half length of disk; ears equal, convex, 

 and ornamented l)y 2 or 3 ol)solete I'adiating ridges and numerous tine incremental 

 lines. Left valve tiat. with 19 prominent convex ribs, a surface scidpture of tine 

 regular incremental lines, and concave ears which are slightly oliliquely truncated. 



D'nnensionn. — Alt. 45 mm.; long. 5;^ mm.; hingi^ line :^iS mm.; diameter ]S mm. 



This species is easily distinguishable by the peculiar shape of the ribs on the 

 right valve. The type (right valve) was collected by INIr. L. D. O'Neal from 

 beds of probat)le lower Pliocene age near Coalinga, Fresno County, and is now 

 in the collection of the Leland Stanford Junior ITniversity. A left valve, which 

 is undoubtedly of this species, was found by Mr. Watts near Kreyenhagen's ranch, 

 Fresno County, and is now in the collection of the California Academy of Sciences. 

 This left valve measures as follows: Alt. 35 mm.; long. 37 mm.: hinge line 13 mm. 



Pliocene (lower). Coalinga, Fresno County (Ij. D. O'Neal); Kreyenhagen's ranch, 

 Fresno County (Watts. Anderson, Arnold). 



Pecten (Pe(^tex) hemphili.i Dall. 



PI. XXXIII. figs. S, %i, and .'«.. 



1879. Pecten hemphilll Dall, Proc. U. S. Nat. Mus., vol. 1, 1S79, p. lo. 



1888. Pecten hemphUli Dall, Cooper, Seventh Ann. Rept. Cal. St. Jlin., 18S8, p. 257. 



1898. Peden {Pecten) hemphilU Dall, Trans. Wagner Free Inst. Sci., vol. S, pt. 4, 1898, p. 70(i. 



1903. Pecten (Pecten) heniphlll! Dall, Arnold, Mem. Cal. Acad. Sci., vol. .3, 190:3, ji. 105. 



Deserlptlon. — Shell of medium size, thin, inequivalve. I'pper (left) valve Hat 

 or slightly concave, with a concave depression lietween middle of \alve and uml)o; 

 surface of this valve sculptured by 16 or 17 ver}- prominent, rather narrow 

 radiating ribs, which are nearly flat-topped and have nearly perpendicular sides: 

 interspaces wider than ribs, with rounding bottoms; tine incremental lamelhe cover 

 the surface of this valve; ears square-cornered and concave, covered with incremental 

 lamellie. Lower (right) valve convex, the convexity being most apparent between 

 middle of valve and umbo; sculptured by KJ prominent squarish ribs, which are 

 similar to those on the upper valve, except that they are slightly broader and have a 

 more rounded top; whole surface sculptured by very fine incremental lines; ears 

 similar to those of upper valve except convex, the right one having 3 or 4 radiating 

 ridges and a small byssal notch. 

 17260— No. 47—06 7 



