388 University of California Publications in Geology [Vol. 8 



PAGE 



Ohrysodomus cereboensis, n. sp 495 



Chrysodomus diabloensis, n. sp 495 



Ohrysodomus pabloensis, n. sp 496 



Siphonalia danvillensis, n. sp 497 



Trophon carisaensis Anderson 497 



Trophon gracilis Perry var. pabloensis, n. var 498 



Trophon dickersoni, n. sp. 498 



Trophon lawsoni, n. sp 499 



Trophon ponderosum Gabb 499 



Trophon ponderosum Gabb var. pabloensis, n. var.? 500 



Murex (Ocinebra) dalli, n. sp 501 



Murex (Ocinebra) paekardi, n. sp 501 



Murex (Ocinebra) selbyensis, n. sp 502 



Cancellaria pabloensis, n. sp 503 



Turris kirkensis, n. sp 504 



Description of Localities 505 



INTRODUCTION AND ACKNOWLEDGMENTS 

 The San Pablo Group, as described in this paper, represents what 

 originally was defined by Dr. J. C. Merriam as the San Pablo forma- 

 tion or beds equivalent thereto. The preliminary work on the paper 

 was begun in the summer of 1910. The writer has been fortunate in 

 having at his disposal the large collections from the San Pablo Group 

 made by the classes in Palaeontology of the University of California 

 Summer Sessions of 1910, 1911, and 1912. These collections were in 

 part made under his direct supervision a"hd in practically every case 

 he has had first-hand knowledge of the field localities. 



In presenting the paper it is realized that many problems have 

 been left unsolved and that much remains to be known concerning the 

 details of the fauna of the San Pablo Group of Middle California. 

 It is hoped that the data given here will form a basis for a more com- 

 plete study of the fauna of this horizon in the near future. 



The writer wishes especially to express his acknowledgment to 

 Dr. -J. C. Merriam, under whose direction the work was begun. A 

 few of the others to whom acknowledgments are due are Professor 

 W. J. Raymond, Professor J. P. Smith, Dr. L. W. Stephenson, Dr. 

 W. H. Dall, E. L. Packard, Harold Hannibal, Bruce Martin, and F. M. 

 Anderson. 



The writer is indebted to a number of persons for collections made 

 in the San Pablo Group, but especially to Dr. John P. Buwalda. Dr. 

 Buwalda, in making a geological section to the east of Walnut Creek, 

 obtained some very fine material from the San Pablo Group in that 

 vicinity. 



