Vol. IV] ANDERSON AND MARTIN— NEOCENE RECORD 23 



The new species and subspecies of marine mollusca described 

 in this paper have been obtained from the middle and lower 

 Miocene of central California and other provinces at various 

 times during the last two or three years. Among the con- 

 tributors of material to this paper have been Mr. R. B. Moran, 

 Mr. W. H. Ochsner, Mr. A. G. Carpenter, Mr. John P. 

 Buwalda, Mr. Charles Morrice, and the writers. The field 

 work and mapping of the San Juan district and the discus- 

 sion of its geology and other features is the work of the junior 

 author. 



NEOCENE RECORD IN THE TEMBLOR BASIN 

 The Temblor Basin 



This basin has already been defined as occupying the larger 

 part of the Central Valley of California and the neighboring 

 intermontane valleys to the west. It is more accurately repre- 

 sented on the map (Plate 9) which shows it bounded on 

 the west and south by the Santa Lucia, San Raphael, the 

 San Emedio and Tehachapi ranges, and on the east by the foot 

 hills of the Sierra Nevada. It is not known to extend farther 

 north than the Marysville Buttes, though Neocene and older 

 Tertiary strata may occur there. An inspection of the map 

 shows the Temblor Basin to be divided by mountain ranges 

 extending through it from southeast to northwest, beginning 

 near the San Emedio Range at the south and extending north 

 to the Straits of Carquinez. These ranges form two groups 

 running nearly parallel, but diverging toward the northwest. 

 Toward the southeast they approach or merge into each other 

 in the region of Coalinga. 



The Mount Diablo Range forms the more easterly group 

 and is more continuous and more important than the other, 

 which includes the San Jose, Gavilan, Santa Cruz and other 

 intervening minor ranges. 



Several small intermontane valleys are enclosed among these 

 mountains, including the Carrizo, Cholame, Peachtree, San 

 Benito, and Santa Clara valleys, and a few others of smaller 

 size. 



Mount Diablo Range. — The Mount Diablo Range embraces 

 a number of minor ranges that are more or less separated and 

 distinct, though having a greater measure of continuity than 



