94 TERTIARY AND QUATERNARY PECTENS OF CALIFORNIA. 



tiiiguishable from the .young of P. kasiafi/s and varieties, except possibly that 

 the ribs on the right valve of Ilinnifes are rather more irregular in size than those 

 of Chlaniyx. 



After comparing Conrad's types of IltitiiifeK rms.w with a large series of living 

 HinnlteK (jujinifeuK, the writer has no hesitation in pronouncing the two species 

 identical. The types of IT. crassa were collected from the upper Miocene near 

 Santa Margarita." (See PI. XXIX, fig. 1.) 



/''. {Ilinii ties) giganU'us VAngt'ti from the lower Miocene to the living fauna. Mr. 

 Eldridge found it associated with Turritella hoffmanni in a small gulch east of 

 Wiley Can\'on, Ventura County. 



RANGE. 



Living. Strait of Fuca to San Diego (Cooper); Quatsino Sound, B. C. (Dawson). 

 Pleistocene. Santa Barbara to San Diego (Cooper); upper and lower San Pedro 



foi'mation, San Pedro (Arnold). 

 Pliocene. Pacific Beach, San Diego (Arnold); Ventura County, Los Angeles County 



(Cooper). 

 Miocene (upper). Santa Margarita, San Luis Obispo County (Conrad). 

 Miocene (lower). Gulch east of Wiley Canyon, Ventura County (Eldridge). 

 Miocene (horizon?) Carrizo Creek district, San Diego County (Bowers). 



PLIOCENE PECTENS. 



[Those known first to appear in the Pliocene formations.] 



Pecten (Pecten) auburyi n. sp. 

 PI. XXXIII, figs. 2 and 2a; PI. XXXIV, lit;,«. .' and 2a. 

 1900. Pecten indet, Merriam, Bull. Cal. 8t. Min. Bureau, No. 19, 1900, p. 222. 



De.senj)iion. — Adult shell averaging about (iO millimeters in altitude, somewhat 

 longer than high, inetiuivahe, plano-convex, equilateral, and with smooth margins. 

 Eight valve convex and ornamented by about 1(5 or 17 prominent, rather narrow, 

 convex-tojjped ribs; intersjjaces slightly narrower than the I'ibs, and with concave 

 bottoms; whole surface sculptured by prominent, tine, sharp, subequal incremental 

 lines; hinge line less than one-half length of disk; ears subequal and convex; 

 anterior ear with two or three obsolete radiating ridges, prominent concentric 

 sculpture, and small byssal notch; posterior ear with concentric sculpture only. 

 Left valve flat or slightly concave, ornamented by 16 or 17 prominent, narrow, 

 convex-topped ribs, which are separated by deep, almost flat-bottomed interspaces 

 slightly wider than the ribs; whole surface sculptured T)y prominent, tine, sharp, 

 equal, concentric lines; ears slightly concave, rectangularly truncated, and sculptured 

 by fine, sharp, concentric lines. 



Dlmenmons. — Alt. 47 mm.; long. 50 nun.; hinge line 21 mm.; diameter 12 

 nmi.; nmbonal angle (left valve) 93^. 



This species is quite closely related to P. li-contei, but is distinguishable from 

 the latter by the smaller angle at the apex (102'^ in the latter), much narrower 

 sharper ribs, and stronger sculpture on the right valve. 



P. auburyi has so far been found only in beds of probable lower Pliocene age. 

 About 1 mile east of the Chandler wells. Puente Hills. Los Angeles County, it is 



