PLATE XXXA IJ. 



I'l.KK'F.NE PKCTENS. 



[I'nloss (ithprwise statod all tiiriircs art.' apiiroxiniali-ly natural size,] 



Page. 



Fk;. 1. {',;-h'ji ( I'lifiiiup.rln,) lua/n/l ii. s|i. U. S. N. M. 14smi'. Type lOS 



Kxti-ri(ir lit' riL'lit valvi^; alfitiiile ll'l iniii. 8an iJivgu foriiiatidii (Pliocene), San Diego 

 Cniinty, Cal. (JNI. 1'. ) 



Fid. l'(. Same ^[u'cinien as Hl'. 1 108 



I'mlile (if riglit valve, as vieweil fmni the rear. ( M. 1'.) 



Fi(i. 2. Perien [ I'litinoiiectni ) healeiii n. s|i. |). .\ ... 103 



Kxterior of a portion of right valve; hinge line .io nnn. I'nrisiiiia Icirmation (lower 

 Plincene), near San (iregorici. San Mateo Cimnty, Cal. (M. P..) 



218 



