PLATE XVIII. 
Vaqueros (Lower Miocene) Pelecypoda. 
(Unless otherwise indicated all figures are one-half natural size.) 
Fig. 1. Pecten (Lyropecten) crassicardo Conrad. U.S.N.M. 164967. Exterior of valve, 
showing characteristic sculpture; altitude 90 mm. Ojai Valley, Ven¬ 
tura County, Cal. This species ranges throughout the Miocene, being 
commoner in the lower part in southern California, in the upper part in 
central California. 
Fig. 2. Pecten ( Amusium ) lompocensis Arnold. Collection of California Academy of 
Sciences. Holotype. Mold of interior of left valve; altitude 105 mm. 
Four miles south of Lompoc. 
Fig. 3. Pecten ( Amusium) lompocensis Arnold. U.S.N.M. 164852. Paratype. Inte¬ 
rior of a portion of left valve; altitude 90 mm. Ojai Valley, Ventura 
County, Cal. 
Fig. 4. Pecten ( Amusium) lompocensis Arnold. Collection of California Academy of 
Sciences. Paratype. Imperfect mold of interior of right valve; hinge 
line 42 mm. Same locality as fig. 2. 
Fig. 5. Pecten ( Lyropecten) bowersi Arnold. Collection of University of California. 
Type. Exterior of slightly imperfect right valve; altitude 150 mm. 
Santa Ynez Canyon. 
Fig. 6a. Ostrea eldridgei Arnold. U.S.N.M. 165320. Left valve; altitude 114 mm. 
View of exterior. El Jaro Creek (4519). Characteristic of this horizon. 
Fig. 66. View of exterior of right valve of same specimen. 
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