PLATE XXXI. 
Miocene Pelecypoda and Gasteropoda. 
(All figures natural size.) 
Fig. 1. Pecten (Lyropecteri) crassicardo Conrad. U.S.N.M. 164967. Exterior of valve, 
showing characteristic sculpture; altitude 90 mm. Lower Miocene, Ojai 
Valley, Ventura County. This species ranges through the lower and 
upper Miocene, being commoner in the former in southern California, in 
the latter in central California. It is sometimes more convex than the 
figured specimen, and often shows concentric undulations of the disk. 
Fig. 2. Pecten ( Chlamys) sespeensis var. hydei Arnold. Collection of Delos Arnold. 
Type. Right valve, ear missing; altitude 46 mm. Lower Miocene, 
Lynchs Mountain, San Luis Obispo County. Found also in the Vaqueros 
formation, Little Sespe Creek, and, with Mytilus mathewsonii Gabb, in 
supposed equivalents of the Vaqueros formation near the Torrey Canyon 
wells, Ventura County. 
Fig. 3. Pecten ( Pseudaviusium) peckhami Gabb. U.S.N.M. 164839. Right and left 
valves in matrix; altitude of largest 17 mm. Monterey shale (middle 
Miocene), southeast of Pinole, Contra Costa County. The type of this 
species came from the Ojai Valley, Ventura County. It is the commonest 
form in the shales of the middle Miocene (Monterey, Modelo, and equiva¬ 
lent formations) and is also known from the Oligocene in the Santa Cruz 
Mountains. 
Fig. 4. Neverita callosa Gabb. U.S.N.M. 164992. View from above, specimen 
slightly tilted; maximum latitude 44 mm. Lower Miocene, head of 
Topanga Canyon, 3 miles south of Calabasas, Los Angeles County. 
Ranges through the Miocene. Common in the lower Miocene of southern 
San Joaquin Valley and the Santa Monica Mountains. 
Fig. 4a. Same specimen as fig. 4. View of base and aperture, showing characteristic 
shape of callous. 
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