PLATE XXXIV. 
Pliocene Pectens. 
(All figures about two-thirds natural size.) 
Fig. 1 . Pecten {Patinopecten) healeyi Arnold. U.S.N.M. 148012. Type. Exterior of 
right valve; altitude 121 mm. San Diego formation (Pliocene), San 
Diego County. A characteristic form in the lower Pliocene from San 
Mateo County to the Mexican line. Left valve with narrow rounded ribs 
and intercalaries; disk also less convex. 
Fig. 2. Pecten ( Lyropecten ) ashleyi Arnold. Univ. California. Type. Exterior of 
right valve; altitude 155 mm. Pliocene, Cerros Island, off Lower Cali¬ 
fornia. Also characteristic of the lower Pliocene, but so far known only 
as far north as Santa Barbara County. The left valve has slightly nar¬ 
rower ribs and no byssal notch in the anterior ear. 
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