4 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4TH SER. 
and sandstones with a very different fauna. ‘Toward the top 
of this lower series the fauna includes: 
Dolium petrosum CONRAD Scaphander 
Nucula truncata GABE Cylichna 
Yoldia impressa CONRAD Leda 
Pseudomusium peckhamt GABB Tellina 
Dentalium 
« 
And still lower in the coniormable series was collected a 
fauna that was referred without a doubt to the Eocene, among 
which were the following: 
Heteroterma trochoidea GABB (?) Pyrula tricostata LAM. 
Rimella canalifera Gasp Aturia angustata CoNRAD 
Urosyca candata GABB 
Mr. Diller adds: ‘Notwithstanding the presence of Aturia, 
which is a characteristic Oligocene form, Dr. Dall refers these 
fossils to the Eocene.”’ 
Writing later of the Oligocene in the United States, Dr. 
Dall’ says: “In the southeastern United States there is no 
marked stratigraphic break between the Eocene and the Oli- 
gocene. Many of the fossils persist into the upper beds, but 
the fauna as a whole undergoes a well-marked alteration, 
showing that physical changes of some sort, such as would 
profoundly affect the fauna, must have taken place. The 
change by which the Oligocene was brought to a close and the 
typical Miocene inaugurated, caused, as already described, 
the most remarkable faunal break in the geological history 
of the United States after the Cretaceous.” 
The stratigraphic relations of undoubted Oligocene deposits 
in California have not been so clearly stated, though there are 
supposed Oligocene deposits on the southern coast that have 
been similarly described. 
Dr. Ralph Arnold* has described Oligocene deposits from 
the Santa Cruz mountains lying below the lower Miocene with 
a fauna which he considers intermediate between typical Tejon 
and lower Miocene. This fauna includes Pecten peckhanu 
and other forms not unknown in the Miocene of California. 
1U. S. Geol. Surv. 18th Ann. Rept. pt. 2, p. 331. 
2U. S. Geol. Surv. Prof. paper 47, pp. 16-17. 
