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AMERICAN JOURNAL 



reply to the separate items at once. Mr. Conrad says I have 

 "included the rock of Canada de las Uvas, which contains 

 Venericardia planicosta and Aturia zic-zac in the Cretaceous 

 series, but he has failed to show one Cretaceous fossil from that 

 rock, and adds:- — "I do not perceive, from Mr. Gabb's Keport, 

 that there is any mixture of Cretaceous and Eocene species in 

 California. 1 ' 



The first proposition I deny; the second I admit, and shall 

 endeavour to prove that it is correct, though from a reason 

 exactly the opposite of the one that Mr. Conrad gives. 



The following list will show the species found in common in 

 the two divisions of the California Cretaceous: — 



Oallianassa Stimpsonii, Gabb, Chico Creek, Div. A. 



Clayton and Tejon, Div. B. 



Shasta Co., A. 



Clayton, B. 



Martinez, A. 



Clayton and Tejon, B. 



Martinez, A. 



Clayton, B. 



Martinez and Mt. Diablo, A. 



Clayton, B. 



Mt. Diablo, A. 



Nautilus Texanusf Shum., 



Aturia Mathewsonii, Gabb, 



Ammonite*, n. s., 



Fusus Mathewsonii, Gabb, 



Amauropsis alveata, Con., sp., 



Denialium Cooperii, Gabb, 



D. stramineum, Gabb, 



Cylichna costata, Gabb, 



Mactra Ashburnerii, Gabb, 

 Aviculx pellucida, Gabb, 



San Diego, Martinez, Clayton, B. 

 Mt. Diablo and Siskiyon, A. 

 San Diego and Martinez, B. 

 Mt. Diablo, A. 

 San Diego and Martinez, B. 

 Almost every locality of both 

 Divisions. 



San Luis Gonza^a, A. 



Martinez, B. 

 Gusullsea Mathewsonii, Gabb, Martinez, A. 



Clayton, B. 

 Nucula (Aci/'i) truncat a, Gabb, Pence's Bancho, Tuscan Sp'gs, 



San Luis Gouzaga, A. 



Martinez, B. 

 Leda protexta (?), Gabb, Martinez, A. 



Nearly everywhere in B. 



The above list contains fourteen species, the identity of sev- 

 eral of which, in the two members of the formation, has been 

 called in question. 



But, granting that Mr. Conrad is correct in every in- 

 stance, there are enough still left to establish the fact, that 

 the two groups of rocks are members of one formation, and 

 not, as he supposes, one Cretaceous, the other Tertiary. 



