Clark: The San Lorenzo Series of Middle California 57 



who have very kindly given the writer access to the Academy's large 

 collections from the Oligocene and Miocene of Oregon and Washing- 

 ton. These collections have been a very great aid to the writer in 

 establishing the relative position of the Oligocene of the region of 

 Mount Diablo. The writer is also indebted to Dr. Dickerson for many 

 friendly criticisms and suggestions. 



Acknowledgment is also due to Dr. Ralph Arnold, who has given 

 the writer charge of his large collections of fossils from the Oligocene 

 and Miocene of Oregon, Washington and Vancouver Island, from 

 which some very valuable data pertaining to correlation have been 

 obtained. 



The following are a few of the others to whom acknowledgments 

 are due : Dr. W. H. Dall, Professor J. P. Smith, Professor A. C. Law- 

 son, Professor G. D. Louderbaek, Professor C. E. Weaver, R. W. 

 Pack, Graham Moody, E. F. Davis and M. C. Edwards. 



REVIEW OF LITERATURE PERTAINING TO THE MARINE 

 OLIGOCENE OF THE WEST COAST 



One of the first descriptions of a geological section on the Pacific 

 Coast was of the Tertiary formations in the vicinity of the town of 

 Astoria, Oregon, and along the Columbia River, by J. D. Dana, 9 who 

 was the geologist of the Wilkes Exploring Expedition. In his report, 

 certain beds in this region, now believed to be of Oligocene age, were 

 referred to the Miocene. The palaeontological work of this expedition 

 was done by T. A. Conrad, 10 who described a number of invertebrate 

 species from the locality above mentioned, some of which may prove 

 to be characteristic of the Oligocene, others of the Lower Miocene. 



A year previous to this, Conrad 11 had published the descriptions 

 of a number of species sent to him by J. K. Townsend from the Ter- 

 tiary deposits on the Columbia River near Astoria. Several of these 

 species have been found to have a wide geographical range, being 

 present in the Tertiary of Washington and California as well as in 

 Oregon. 



During the years 1854 and 1855, the fifth, sixth and seventh 

 volumes of the Pacific Railroad Reports were published. The palaeon- 



9 Dana, J. D., Geol. U. S. Expl. Exped., vol. 10, pp. 626, 652-654, 657-659, 

 1849. 



10 Conrad, T. A., Fossils from northwestern America, Geol. U. S. Expl. Exped., 

 vol. 10, app. 1, pp. 723-729, pis. 17-20, 1849. 



11 Conrad, T. A., Fossil shells from Tertiary deposits on the Columbia Kiver 

 near Astoria, Amer. Jour. Sei., ser. 2, vol. 5, pp. 432-433, 1848. 



