EXPLANATION OF PLATE 4 



Pig. 1. Pecten viclceryi, n. sp. X 1. Left valve. Type in Stanford Univer- 

 sity Paleontological Collection. Briones. 



Fig. 2a. Spisula falcata brioniana, n. var. X 2. Eight valve, showing 

 dentition. Type.— No. 12380, Univ. Calif. Mus. Pal., loe. 3522. Briones. 



Fig. 2b. Spisula falcata brioniana, n. var. X 2. Exterior view. Type. 



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