1913] DicJcerson: Fauna of Eocene at Marysville Buttes 271 



In the total list of sixty-five species a total of only thirty-one 

 are reported from other Tejon localities. Nearly all of these 

 forms, as the table shows, have a wide geographic range. The 

 partial list of species collected by Brace Martin from the Umpqua 

 formation, given under the description of Turritella merriami, 

 (p. 287), shows that many of them are found in the Eocene of 

 Oregon. Many of these forms have also a great stratigraphic 

 range. The exact range of some of these species is not known. 

 Carclium cooperi is probably the progenitor of Cardium dalli 

 Trocliocyathus striatus occurs in the San Francisco Bay region 

 above the coal strata north of Mt. Diablo and in uppermost 

 Tejon, south of Mt. Diablo where it is associated with Card in in 

 cooperi. This suggests that the uppermost Eocene of the Marys- 

 ville Buttes is younger than that of Mt. Diablo Region. Without 

 doubt the beds at Marysville Buttes are Eocene but their fauna 

 apparently represents a faunal zone which lias not been recog- 

 nized elsewhere. This faunal assemblage has over thirty species, 

 which have not been found at other localities. 



It has been shown that the peculiar aspect of the Marysville 

 Buttes fauna is not due solely to local facies of climate, or of 

 habitat along an open ocean. Life in relatively deep water no 

 doubt influenced its development, but this factor does not explain 

 the great difference between this fauna and that found in the 

 uppermost Tejon of the Mt. Diablo region. As nearly as can 

 be determined, the peculiarities of the Marysville Buttes fauna 

 are due in some measure to its having lived in a division of 

 Eocene time from which no adequate representation of the 

 marine life of the Pacific Coast has been known up to the 

 present time. Evidence that the Marysville Buttes collections 

 represent a zone slightly different from the uppermost Tejon of 

 the Mt. Diablo region is found in the fact that his assemblage 

 differs much more from the Martinez fauna than does the fauna 

 of any portion of the typical Tejon. This would indicate 

 that the Marysville Buttes zone is removed from the Mar- 

 tinez by a longer period than is the typical Tejon. That the 

 Marysville Buttes fauna is later than the Martinez and chiefly 

 later than the typical Tejon is shown ( 1 ) , by the absence of such 

 genera as Cucullaea, Anchura, Heterotcrma, Urosyca, and Her- 



