EXPLANATION OP PLATE 54 



All figures approximately natural size 



Fig. 1. Venus martini, n. sp. A common species in the Astrodapsis whitneyi 

 zone. 



Pig. 2. Pitaria behri, n. sp. Anterior view. Showing lunule on posterior 

 dorsal area. 



Pig. 3. Pitaria behri, n. sp. Left valve. Longitude, 64 mm. 



Pig. 4. Pitaria behri, n. sp. Hinge plate of left valve. 



Fig. 5. Tivela diabloensis, n. sp. Interior view of right valve. 



Fig. 6. Tivela diabloensis, n. sp. Exterior view of same specimen as figure 

 (3. Longitude, 59 mm. 



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