EXPLANATION OF PLATE 6 



Fig. la. Tivela merriami, n. sp. X 1. Eight valve, exterior view. Type. — ■ 

 No. 12378, Univ. Calif. Mus. Pal., loc. 3582. Briones. 



Fig. lb. Tivela merriami, n. sp. X 1. Eight valve of type, showing den- 

 tition. 



Fig. 2. Trophon gracilis clarki, n. nom. Type. — No. 11625, Univ. Calif. Mus. 

 Pal., loc. 409. Lower San Pablo (Cierbo). 



Fig. 3. Trophon gracilis clarki, n. nom. Cotype — No. 12390, Univ. Calif. Mus. 

 Pal., loo. 177. Briones. 



Fig. 4. Trophon gracilis clarki, n. nom. Cotype. — No. 11626, Univ. Calif. Mus. 

 Pal., loc. 409. Lower San Pablo. 



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