1916] 



Dickerson: Tejon Eocene of California 



367 



unconformity upon the rocks of the underlying' formations, but strati- 

 graphic relations to the overlying formations are not always so clear. 

 The Oligocene as represented by the Agasoma gravidum zone does 

 not always appear to be sharply set off from the Tejon. Recent 

 studies in the southern end of the Great Valley made by Clark Gester 

 at San Emigdio and John Ruckman at Coalinga appear to show inter- 

 gradation between the two groups. Faunally, however, the Tejon is 

 distinct from both the Martinez Eocene below and the Agasoma grav- 

 idum zone (Oligocene) above. 



The lone formation of the Sierra Nevada foothill region is the 

 uppermost member of the Tejon group and, as will be shown later, 

 is the marine equivalent of a great portion of the Superjacent series, 

 the land and stream-laid deposits of the Sierra Nevada. 



ACKNOWLEDGMENTS 



The writer is indebted to Mr. J. A. Taff and to Mr. G. C. Gester 

 of the Southern Pacific Company for the facilities of their camp on 

 Salt Creek and for their guidance in the field to the best collecting 

 localities. It was the intention of Mr. Gester and the writer to describe 

 the Cantua region in a joint paper, but this was prevented by Mr. 

 Gester 's departure for Peru. The faunal relations are so important 

 that it was thought best to publish these results now and the complete 

 stratigraphic discussion later. 



The Tejon collections made by the December, 1913, field party of 

 the Department of Palaeontology of the University of California were 

 turned over to the writer by Dr. B. L. Clark and Mr. John Ruckman. 

 The writer is especially indebted to Professor J. C. Merriam for the 

 opportunity to make this investigation and for his kind criticism 

 during its progress. 



The writer has been assisted in this work by many persons. Pro- 

 fessor J. C. Merriam, Dr. B. L. Clark, Dr. J. P. Buwalda. Dr. E. L. 

 Packard, Mr. W. S. W. Kew, Mr. J. Ruckman, Mr. W. Gordon and 

 other members of the 1911 and 1912 Summer School classes in 

 Palaeontology rendered much help in the work in the Mount Diablo 

 region. 



REVIEW OF THE LITERATURE 



The literature of the Tejon group is so voluminous that only the 

 principal papers will be reviewed. These papers deal with age, fauna, 



