Geol— Vol. II.] ANDERSON— CRETACEOUS DEPOSITS. 49 



Chico deposits. It might also be said that the Lower Chico 

 has a wider transgressional expansion than the other. 



Quite similar relations exist also between strata of the 

 Lower Chico and Horsetown epochs, with the difference, 

 however, that in California the Horsetown is but little known 

 outside of the Sacramento Valley, or to express it more 

 accurately, outside of the immediate borders of the Great 

 Valley. Its distribution is apparently restricted, just as are 

 the deposits of the sub-Knoxville, almost entirely to this 

 basin, where it builds with the strata of the lower and upper 

 horizons of the Cretaceous a more or less continuous series. 

 The fact is a remarkable one, that throughout the Coast 

 Ranges west and south of the Great Valley, few if any 

 deposits of Horsetown age are found. Those that have 

 been satisfactorily shown to belong to this epoch lie upon 

 the immediate borders of the Great Valley, and they have 

 yet to be found south of the latitude of Benicia and the 

 junction of the two great rivers of this basin. 



There is no assignable reason why deposits of the Horse- 

 town should not be found within the boundaries of the San 

 Joaquin Valley, but as yet the nearest approach to this fauna 

 that has been discovered south of the latitude named is from 

 a locality lying about eight miles east of the town of Liver- 

 more, at Arroyo del Valle, some miles southeast of Mount 

 Diablo. This is a locality discovered many years ago by 

 Dr. Lorenzo G. Yates of Santa Barbara, who obtained 

 from this place a large number of ammonites now in the 

 collections of Stanford University. Among them are the 

 following species as determined by Dr. J. P. Smith: — 



Baculites chico'ensts Lytoceras cf. L. tinwtheaniim 



Belemnites sp. Pachydiscus cf. P. newberryayius 



Cinulia obliqua Pachydiscus cf. P. suciaensis 



Desmoceras hoffmanni Phylloceras onoense 



Desmoceras cf. D. selwynanimi Phylloceras raniosiini 



Hoplites remoiidi Placenticeras californicuni, sp. nov. 



Lytoceras alamedense Placenticeras pacificmn 

 Lytoceras batesi 



It can not be denied that the fauna of this locality shows 

 a strong intermingling of Horsetown and Lower Chico 



