76 TERTIARY AND QUATERNARY PECTENS OF CALIFORNIA. 



Between San Lucas and San Ardo. Monterey County. jVIr. Homer Hamlin 

 found a specimen of P. I'dreJlanus measuring 125 millimeters in altitude, which 

 shows the striations well developed on the anterior and posterior ribs and near the 

 ends of the middle ribs and interspaces. The flat forms grading into var. catalinae. 

 were found associated at this locality with the typical convex shells. 



In central California, especially in the region about the Salinas Valley, the 

 P. estrdhmuK associated with the large Ostrea titan Conrad usually have nineteen 

 ribs, while those found in the horizon of Ostrea palmiila^ Carpenter and Chorus 

 helcheri Hinds average two or three less. The latter horizon appears to be above 

 that of O. titan. 



In the region around Coalinga. Fresno County, P. estreUanus is very common, 

 and is usually associated with Tainiomina grcyaria^ Ostrea titan, Venus jjertenuis, 

 Cliione n. sp. (large; coarse sculpture). Area canalis, etc., in beds which may be the 

 equivalent of the San Pablo formation. The significance of the total absence of 

 P. estrellanus from the type locality of the San Pablo is not at present known. 



So far as is definitely known, this species is confined to the Miocene, where it is 

 found in nearly every county of California from Napa to Orange. In some places 

 it is found associated with a characteristic lower Miocene fauna, while at others the 

 same form will be found in the San Pablo or upper Miocene. 



RANGE. 



Miocene. Napa County (Lockwood); Solano County (Cooper); Alameda County 

 (Yates); Mount Hamilton Range (J. P. Smith; Arnold); Santa Cruz Mountains 

 (Ashley; Arnold); San Lucas and San Ardo, Monterey County (Ander.son; 

 Hamlin); Lynch's Mountain, ^Monterey County (C. S. Smith); 15 miles north- 

 east of San Miguel, Monterey County (Hamlin; Arnold); San Luis Obispo and 

 Santa Barbara counties (Conrad; Fairbanks; R. Moran; J. H. Wilson; Arnold, 

 and others); Coalinga, Fresno County (Watts; Eldridge; L. D. O'Neal); San 

 Benito County (Turner); Santa Ana Range, Orange County (Watts); El Toro, 

 Orange County (Bowers). 



Pecten (Lyeopecten) estrellanus Conrad var. catalin.*; n. var. 



PI. XX, figs. 3, 3a, and 4. 



Description. — Shell averaging about 65 millimeters in altitude, considerably 

 longer than high, equivalve, equilateral, of medium tliickness, only slightly 

 ventricose, and with margins more or less serrate; base evenly rounded; sides 

 only slightly concave above. Right valve with 19 or 20 square, flat-topped ribs, 

 all of which are sculptured 1)y incremental lines and the 3 or -t outer ribs on 

 each side by more or less prominent radial lines; inteispaces narrower than ribs 

 and ornamented by a prominent squarish riblet; hinge line over one-half length 

 of disk; anterior ear arcuate in front, with rather small byssal notch, and orna- 

 mented by concentric lines and 5 or 6 rather prominent radiating ridges; poste- 

 rior ear with concave end and ornamented by numerous fine radiating ridges and 

 incremental lines. Left valve similar to right except that the ears are both like 

 the posterior one of the right valve, and the interspaces are relatively a little 

 wider. 



