272 University of California Publications in Geology [Vol. 7 



coglossa; (2), by the presence of such genera as Bittium, Cor- 

 diera, Cancellaria, and Drillia; (3), by the occurrence of such 

 species as Trochocyathus striatus, Tritonium calif ornicum Cor- 

 bula parilis, Glycimeris cor, Tapes conradiana, Oliverato cali- 

 fomica, and Cardium dalli, n. sp. 



Of the first mentioned genera Cucullaea and Anchura are 

 characteristic of the Cretaceous and of the earliest Eocene on 

 this coast. Heteroterma and Urosyca are wholly restricted to 

 the Martinez. Since none of these genera are represented in the 

 Marysville Buttes Eocene, the fauna is evidently not pre- 

 Martinez. Bittium, Cordiera, Cancellaria, and Drillia are all 

 represented in stages ranging from the late Eocene to the Re- 

 cent. Since they occur in the Eocene strata of the Marysville 

 Buttes, it is evident that this fauna is a phase of the later Eocene 

 or Tejon, as they are certainly more characteristic of the later 

 Eocene than they could be of any horizon inferior to the early 

 Eocene of the Martinez stage. The species mentioned above all 

 occur in the uppermost Tejon of the Mt. Diablo region except the 

 last, whose precursor, C. cooperi, is found there. Trochocyathus 

 striatus is restricted to the upper portion of the Tejon of this 

 locality. Cardium, dalli, n. sp., seems to the writer to have 

 evolved from C. cooperi and hence to have lived at a later time. 

 The unique character of the Marysville Buttes fauna appears to 

 be due to its representing a period from which no adequate fauna 

 had previously been obtained and not to depth of water, climate, 

 or other causes. That it evolved from the typical Tejon there 

 can be little doubt. We are led to the conclusion that the 

 Marysville Buttes fauna is not only further removed from the 

 Martinez than is the typical Tejon, but that the distance remov- 

 ing it from the Martinez is measured toward the Recent fauna. 

 In other words the evidence indicates that the Marysville Buttes 

 fauna represents a later zone or stage of the Eocene than the 

 typical Tejon. 



