MIOCENE PECTENS. 79 



Balanus (cf.) estrellanux, Cardium {Trachycardium) n. sp., Chione mathevwmii, 

 Chione n. sp. (large; coarse sculpture), Crepidida jyi'inceps, Cunia bipUcata, Dos'mia 

 conradi, Dosinia matheimonii, Dosinia {cf.) montana^ Dosinia {aff.) ponderosa, Gale- 

 rus {((ff.) eccentricus., Glycymma n. sp. (large), PhacoideH acutilineatuf<^ Phacoides 

 richthofeni. My til us mathewmn'il., Nererrta rechuziana, Ostrca (aff.) titan, Panoj>ea 

 generosa, Pecten estrellanus, Pecten {Phicjiocteniuin) andenwd, Solen sicarius, Tivela 

 ineziana, Trnchita costellata, TurriteUa Juffinanni. On the south fork of the lower 

 Ojai Valley. Ventura Count}', Mr. Eldridge found I', 'in.agnolia associated with 

 Chione n. sp. (large; coarse sculpture), Mytilus m.atheivsonii, Turritdla hiffniuiiui, 

 Pecten sespeensis var. hydei, and other lower Miocene forms. * 



Miocene (lower). Mindego Creek, 10 miles south of Stanford University (Arnold); 

 Corral de Piedra Creek, San Luis Obispo County (J. H. Wilson; Robert Moran; 

 Fairbanks); Hazard Canyon, 12 miles southwest of San Luis Obispo (N. H. 

 Drake); Morro and Toro creeks, San Luis Obispo C'ounty (Fairbanks; R. 

 Moran); Santa Inez Mountains, Santa Barbara County (Conrad); near Oceanic 

 quicksilver mine, San Simeon, San Luis Obispo County (L. Wagner); Ojai 

 Valley, Ventura County (Eldridge). 



Pecten (Ltkopecten) miguelensis n. sp. 



PI. XXII, iig.«. 1, lo, and Ih; I'l. XXIII, tig. 1. 



1898. Pecten { Li/ropecten) Heermanni Dall, (not Conrad) , Trans. Wagner Free Inst. Sci., vol. .S, pi. 4, p. 

 701. (Specimens in U. S. Xat. Mus., No. 6397, labeled F. Heermanni by Conrad; PI. XXIII 

 fig. 1.) 



Description. — Shell averaging about 110 millimeters in altitude, about as long as 

 high, inequivalve, subequilateral, rather thin, and with margins more or less serrate; 

 base rounded; sides slightly concave above, the posterior being slightly longer than 

 the anterior. Right valve more convex than the left, with 17 or 18 prominent 

 rounded ribs, each sculptured by several (10 or 11 at extremity of ribs in type) dis- 

 tinct radiating raised riblets and numerous sharp, minutely wavy, incremental lines; 

 interspaces narrower than ribs, and containing by a prominent radial auxiliary rib, 

 which is ornamented by the incremental sculpture, and toward the periphery of the 

 disk, by two or more radiating riblets as in the large ribs; hinge line somewhat 

 longer than one-half the length of the disk; anterior ear arcuate in front, with small 

 byssal notch, and .sculptured by 5 or 6 prominent, rounded, radiating ridges and 

 numerous sharp, concentric lines; posterior ear with 10 or 11 radiating riblets and 

 fine incremental sculpture. Left valve less ventricose than the right, but otherwise 

 similar to it, except that the ribs are slightly narrower and the interspaces relatively 

 broader; ears similar to those of the right valve except that the anterior one lacks 

 the byssal notch. 



Dimensions. — Alt. 107 mm. ; long. 110 mm. ; hinge line 60 mm. ; diameter 50 mm. 



This species is distinguishable from P. estrellanus and others of the same group 

 by its larger size, inequality of valves (which are more or less inequilateral), and 

 radially striate surface from umbo to periphery. It sometimes shows the constric- 



