1913] Dickerson: Fauna of Eocene at Marysville Buttes 267 



which range from low water to 100 fathoms was decidedly 

 noticeable when the collection listed above was made. The 

 lamellibranchs were, except Nucula, Leda and Cardium, very 

 rare. 



The evidence taken as a whole leads to the conclusion that 

 the glauconitic sandstones and shales were laid down in water 

 about 100 fathoms deep. 



Climatic Conditions During Accumulation op Marysville 



Buttes Eocene 



Another factor which must be considered in connection with 

 this unique fauna is the climate at the time of the deposition of 

 the sediment containing it. Dr. Cooper 13 in describing Turris 

 monolifera makes the following note: "The occurrence of seven 

 new pleurotomidae without many other univalve shells, and 

 especially the absence of many forms of genera allied to Fusus 

 described by Gabb, is a condition of distribution indicating prob- 

 ably that a warmer sea existed where they are found than at most 

 localities of similar age in California. " Thorough collection does 

 not sustain his view entirely. The number of Pleurotomidae is 

 noteworthy, but they are associated with twenty-eight other 

 univalve shells and seventeen lamellibranchs. Several of these 

 gastropods are allied to Fusus. He was comparing a fauna which 

 is not essentially littoral to species which are found in a por- 

 tion of the Chico, the Martinez, and the Tejon. The writer is 

 in thorough agreement with this suggestion of a warmer climate 

 during the deposition of the Eocene of the Marysville Buttes, but 

 the littoral or shallow water fauna of the typical Tejon also sug- 

 gests a warmer climate than that of the present day. Several 

 of the species, Voluta lawsoni, Tapes conradiana, Oliverata cali- 

 fornica, Sureula crenatospira and Cardium dalli, still retain high 

 coloring suggesting strongly the tropical forms of today. Sev- 

 eral of these genera are according to Tryon confined to or char- 

 acteristic of tropical and snb-tropical waters. Among these are 

 Voluta, Siphonalia, Turris, Sureula, Drillia, Tercbra and Can- 

 eellaria. 



is Cooper, Dr. J. G., California State Mining Bureau, Bull. No. 4, Cata- 

 logue of California Fossils, pp. 39-40. 1894. 



