MIOCENE PECTENS. 71 



toward the apex; byssal notch wide and of medium depth; posterior ear rectan- 

 gularl}' truncated, radiatel\- ribbed, and cros.'sed 1)\' confciitric incremental lines. 

 Left valve prominently and evenly ventricose; sculptured the same as the right 

 valve except that most of the interspaces contain an auxiliary riblet; antei-ior ear 

 arcuate ended, radiately ribl)ed, and with concentric incremental sculpture; posterior 

 ear as in right valve. 



Diiiicnxidn-i. — Alt. 150 mm.; long. 150 mm.; hinge line (restored) 90 mm.; 

 diameter 55 mm. 



This species is distinguishable by its large size, almost smooth rounded ribs, 

 and the greater convexity of the left valve. The flat surface of the right valve 

 near the apex is also a very noticeable characteristic. P. Ixjwersi is placed in the 

 section Lyropecten because of its hinge and general aflinity to the group. It, 

 however, lacks the radial secondary sculpture found developed to a greater or less 

 degree on most of the species of this group, and is also different from the other 

 members examined by the writer in having the left valve noticeably the more 

 convex. 



P. hnvers/' ranges from the lower to possibly the middle Miocene, being found 

 associated in some localities with 7\ magnol/'d, and in others with J', disri/.s. 



The type which is tigUred is from Santa Inez Canyon, Santa Barbara County, 

 and is now in the collection of the University of California. Named in honor of 

 Dr. Stephen Bowers, of Los Angeles, one of the pioneer geologists of southern 

 California, to whom the writer is indebted for much valuable material and infor- 

 mation used in the preparation of this paper. 



Miocene (middle;^). Gillis's ranch, 10 miles southwest of Paso Robles, San Luis 

 Obispo Count}' (J. P. Smith). 



Miocene (lower). Santa Inez Canyon, Santa Barl)ara County (Voy; J. H. Wilson); 

 La Panza Creek, San Luis Obispo County (Fairbanks; R. Moran; Arnold); 

 Barker ranch, and ''top of hill" at Long Tom mine and Miller Bros, ranch 

 east of Annette P. O., Kern County (Watts; Arnold); 30 miles north of Santa 

 Monica and 1 mile from ocean, Ventura County (R. E. Maj'nard); Santa Monica 

 Mountains, Los Angeles and Ventura counties (Bowers). Station No. 550, 

 Santa Ana Mountains (Watts). 



Pecten (Lvropecten) cra.ssicardo Conrad. 

 PI. XVI, figs. 1 ami hi; PI. XVII, figs. 1, \a, and l/>; PI. XVIIl, figs. 1, 2, and 2a. 



1856. Palliuin cnissicardo Conrad, Proc. Acad. Nat. Sci. Phila., 1856, p. ;>lo. 



1857.? Spondylus [=Pf'cte)i] EstrallensU Conrad, Proc. Acad. Nat. Sci. Phila., first series, vol. 8, for 



1856, 1857, p. 315. 

 1857.? Spondylus [=Pecten] Estrellanus Conrad, Pac. R. R. Rept., vol. 7, 1857, p. 191, pi. 1, fig. 3; not 



Pallium [=Pecleii] estrellimum Conrad, Pac. R. R. Repi., vol. 6, pt. 2,1856, p. 71, pi. 3, fig. 15. 

 1863. Pecten crasdcardo Conrad, Proc. Acad. Nat. Sci. Phila., 1862, p. 291. 

 1867. Lyropeclen crassicardo Conrad, Am. Jour. Conch., vol. 3, 1867, p. 6. 

 1869. Livopecten crassicardo Conrad, Gabb, Pal. Cal., vol. 2, 1869, p. 105 (in part, at least). 

 1888. Liropeden crassicardo Conrad, Cooper, Seventh Ann. Rept. Cal. St. Min., 1888, p. 246 (in part, 



at least). 



