PLIOCENK PECTENS. 121 



riblets in the wide interspaces. The specimens of /'. wattfl are too poorly 

 preserved to show satisfactorily the mii'roscopic sculpture of the surface, but 

 what is left of this sculpture appears to Ix' vci-y nuich like that of /'. xinft/i. 



/'. iwittis/ differs from P. parineleei in liaving- broader and more strongly 

 nodose ribs, more numerous (6 instead of 4) radials on the anterior ear, and 

 most of all bj the fewer and much larger-sized secondary radial riblets in 

 the major interspaces. The poor state of preservation of the type of /'. imMsl 

 precludes any definite statements regarding its micM-oscopic surface sculpture, but 

 from as good a comparison as could be made under the circumstances the two 

 .species appear to have somewhat different kinds. 



P. iimtU'i is found in beds near Kreyenhagen's ranch, Fresno County, which 

 are supposed to be of lower Pliocene age. It has })een collected from beds of 

 lower Pliocene age (Purisima formation) on Pescadero Creek, San Mateo County, 

 and at other localities in the southern part of the State. At Olinda, Puente Hills, 

 Orange County. .Mr. Eldridge found /■'. wtittsi. associated with P. (ishli-yi. 

 P. attburyi, P. oweiii var., Prloie {(iff.) oregonennix, Oardlitm (<■/■) quudrujena- 

 riuiii, yeverita reditzinna, Phaco'i(iei< californicus^ and FiimiK (ef.) harhareni^is. in 

 beds of pro))able lower Pliocene age. 



The type is from Kreyenhagen's ranch, Fresno County, and is now in the 

 collection of the California Academy of Sciences. It is named in honor of 

 Mr. W. L. Watts, whose collecting has added very materially to the list of west 

 coast fossil Pectens. 



KANGE. 



Pliocene (lower). Pescadero Creek, one-fourth mile above Jones Gulch, San Mateo 

 County (Newsom; Arnold); Kreyenhagen's ranch, Fresno County (Watts); 

 Olinda, Puente Hills. Orange County (Eldridge). 



Pectex (Ciilamys) wattsi var. mdhani n. var. 



PI. X, tigi^. 3, 4, .i, and (_i. 



Description. — Adult shell averaging about 65 millimeters in altitude, much 

 shorter than high, iiiequivalve, equilateral, moderately convex, and with slightly 

 serrate margins. Right valve less convex than the left, ornamented by 4 very 

 broad, prominent, tiat-topped ridges, each of which carries from 5 to 7 strong, 

 squarish, elevated, subequidistant riblets; intersjDaces narrow and rather deep, each 

 ornamented ])y 1 or 2 squarish riblets: hinge line about one-third length of disk: 

 anterior ear much more prominent than the posterior, regularly arcuate-ended and 

 sculptureil by .") or ti radials; by.s.sal notch only slightl}- developed; posterior ear 

 very short, ol)liquely truncated and radially striate. Left vahe more convex than 

 right, and usually more or less undulated by constrictions; disk with 5 subequal, 

 narrow, ridgc-like ribs, separated by wide interspaces, in each of which are from 

 2 to 5 subeijual, prominent, squarish riblets; whole surface ornamented by a 

 superimposed tessellation, which is usually worn off' in the adult shells; ears 

 similar to those of the right valve, there being nearly as pronounced a byssal 

 notcli in the anterior ear of the left valve as in the anterior one of the rio-ht. 



