EXPLANATION OP PLATE 23 



All figures natural size. 



Fig. 1. Spisula occidentalis (Gabb). Miocene. 



Fig. 2. Spisula occidentalis (Gabb). Miocene. 



Fig. 3. Spisula occidentalis (Gabb) . Miocene. 



Fig. 4. Spisula abscissa (Gabb) . Miocene. 

 Left hinge. 



Fig. 5. Spisula albaria (Conrad), var. ramonensis, n. var. Miocene. 

 Hinge of left valve of cotype. 



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