P I. A T E X X AM T . 



MK.K'KXK I'KCTICNS. 



[I'lik'ss DllnTwivc ^tat^•ll nil liirnrrs ;n\' :ip|ir(ixini;ilrl\ natural sizf.] 



I'as;.-. 



Fi(i. 1. Pecteii {J'l(i(/ii)rlniiiiiii ) ilisnis Conrad, l'. (' .sti 



Extericir of left \al\ c ( aiilcrior ear slightly hroUcn j ; altitu'lc 4i; luiii. !\lioci'iu' ' iipiicr ), 

 Walnut ('r(_'el<. Contra Costu County, Cal. (S. ) 



Fiii. 1(/. Same specinjcn as lit;. I Ml 



Profile of left valve as viewed from the rear. I M. I'. I 



Fui. •_'. Pi'ck'ii [I'liiijiiM-li'iiiiiiii^ (/I'.wK.s Conrad. V. S. X. M. i:;:!:;."). Type .SO 



Copied from adrauiiit;' hy l>oitor !\leConnell of a sli.uhtly contorted eas^t of the exterior 

 of a left valve; altitude 47 nun. .Miocene, Ventura County, Cal. 



Flii. :!. I'icli II ( I'liigiurtcniinii I illnrns ( 'onrad. L. S. J. U Hli 



Wax east of exterioi- of riudit valve; altitude ?>0 nun. Miocene, .Santa Marin. Santa 

 Barbara County, Cal. i .M. P. 1 



Fiii. 4. JWteii ( P/'ii/iiirhiiiiiiii] ilisriit: Courad. 1>. A 86 



Mold of exterior of imperfect right valve: hinge line 'J4 mm. .Minci'iie, lietween Mono 

 and Little Morro creeks, San Luis t)liis]io ('■■imty, Cal. |M. I!. I 



Flo. ."i. Pirlcri [ P/di/ioclenitim ) jiiihliii'iisU Conrad. 1 r .\ SS 



Exterior of left valve; altitude :'.4 mm. San I'nliln fm-unilion i upper Miocene I, San I'nlilo 

 Bay, Contra Costa County, Cal. i M. 1'. ) 



l>"ii:. rill. Same specimen as lig. o SS 



Profile of left valve as viewed from tli<' renv. ( M. P. ) 



Flo. (i. I'irti'ii {Pliii,in<-lniiiiiii ) iial.lnriisis Conrnd. 1 1. .\ SS 



Exterior of imperfe{'l right v.ilve; altitude .'il.' nun. Same loi-ality as lig. .">. ^M. P.) 



Flo. 6((. Same specimen as (ij:. li S8 



Profile of right vahi' as \ iewed from the rear. ( M. P. ) 



I'lo. 7. I'irti'il ( PhlijiiirUiiiniii I pillilnriixis C.inrad. 11. A SS 



Exterior of right vaKi' of a young specimen, showing prominence of rihs near umho; 

 altitude 24 mm. Same Imality as tig. .">. ( .M. P. 1 



Flo. 8. Pertini {Paeudiiiiiiisiuiii) luiiipii'iiciisis i\. sp. U. S. N. M. UUKIil. Tyj)e S!i 



Mold of exterior of right (tyj)!') and left valves and imperfect cast of exterior of viuhl 

 \al\e; allitude of mold of ri'_dit valve, I 1 .."i nmi.. • '■':. Miocene shale, head I'f Lnmpico 

 Creek. Santa Cruz County, Cal. (M. B. ) 



198 



