120 TERTIARY AND QUATERNARY PECTENS OF CALIFORNIA. 



Right valve unknown, imt. jiulging- hy the atHitity whicli this .species Vjear.s to 

 P. ixli(i)dl<-ii.'<. it sliould i)c siniihir to tlio .l(>ft valve, with the exception that the 

 anterior ear should have a dei'p hvssal notch, and the ribs should be slightly 

 broader and the interspaces correspondingly narrower. 



Dimeuiiioiis. — Alt. llo nini.: long, about loo mm.; hinge line about 30 mm.; 

 diameter 30 mm. 



This species is closelv allied to /'. ixIdinlicuK. and nr.iy be its direct precursor. 

 It is distinguishable from the latter, however, by its larger size (tieing the largest 

 species of this group yet known from the Pacific coast), more numerous, lower, 

 and smoother ribs, and less obliquely truncated posterior ears. 



P. v;ux]ihurn<-i occui's in beds on the Yachates River, Lincoln County, Ort'g., 

 where it is a.ssociated with the following fauna: Opal'xi cditdtmi Dall, Tviu-hmteJIn 

 transversa Sbv, Aemwa sp., StrDiigylocentrotns {<•/.) piirpunitiis Stimpson, Cidarix 

 (i) sp., Xati-ca or Ni'verita sp., Bupcmuvi ('() sp.. ('idlioxtoiiai sp. Doctor Dall is 

 of the opinion that the.se beds are the equivalent of those at Eugene, Oreg., of 

 who.se position in the stratigraphic column there is much uncertainty. Tentatively, 

 however, this species will be ])laced with those from the lower Pliocene. 



This .species is named in honor of Mr. Chester Washburne, of Eugene, Oieg., 

 whose work in the Oregon Tertiary has added many new .species to the li.sts. 

 The type is now in the C S. National Museum (No. Itl4.s4:3). locality S.M^S. 



Pliocene (lower^). Yachates River, Lincoln County, Oreg. (Washburne). 



Pecten (Chla-Mys) wattsi n. sp. 



PI. XI. tigs. 1 an.l \<i. 



DiiSiyi'iptioit. — Shell a\-eraging about ().5 millimeters in altitude, slightly higher 

 than long, ecjuilateral, of medium thickness, decidedly ventricose, and with margins 

 slightly finely serrate; base regularly rounded; sides sloping above, with slight 

 concavity. Left valve with 5 high, rather narrow, rounded, almost smooth ribs, 

 which are made prominently nodose l>y several very pronounced concentric undula- 

 tions, or constrictions; interspaces much wider than ribs and each ornamented l)y 

 about .5 small, suttequal, rounded, imbricated riblets; whole surface of disk with a 

 ))rofuse, coalescent, microscopically checkered squamation; hinge line about two- 

 tifths length of disk; anterior ear with arcuate end. and with surface sculptured by 

 about .5 prominent imbricated riblets and several concentric undulations; posterior 

 ear obsolete. Right valve alxnit equal to left in convexity, with broad. Hat topped 

 ribs and narrower interspaces, both being longitudinally sculptured by subequal 

 riblets; ears similar to left; by.ssal notch not prominent; surface sculpture micro- 

 scopic; constrictions less pronounced than in left valves. 



Duiiciisioiis. — Alt. 67 mm.; long. .5;t mm.; hinge line 20 mm.; diameter 36 mm. 



This species is even more closely allied to P. s'lDiftii. Bernhardi (Jour, de 

 Conch., vol. 7, 1S5S, p. !»<•, pis. i and ii), of Japan, than is P. parmeleei. It is 

 distinguishable from /'. .-mufti i, however, by its broader ribs, not alternated 

 radial riblets on the right anterior ear. and by the smaller number of .secondary 



