Geol— Vol. II.] ANDERSON— CRETACEOUS DEPOSITS. 69 



persistent forms have survived from one epoch to the next. 

 The faunal evidence of such disturbances is reinforced by 

 the abundance of conglomerates which are interstratified 

 with sandy and shaly beds, especially in the upper portion 

 of the series. Coincident with the evidence of these facts 

 is that of the territorial distribution of different members 

 of the series in California and Oregon. 



The Cretaceous series of the Sacramento basin and of 

 the whole Pacific border (excluding the Sub-Knoxville, 

 which is probably of pre-Cretaceous age), is divisible into 

 the following well defined members: (i) The Knoxville 

 horizon, including several thousand feet of strata extending 

 upward to the upper limit of the present known species of 

 Aucella, embracing what has been shown to be essentially 

 a boreal fauna; (2) the Horsetown horizon, beginning 

 with the close of the Knoxville and the substitution of a 

 typical subtropical fauna for one of boreal character, and 

 continuing to the horizon representing the great Chico 

 overlap; (3) the Chico, or uppermost member of the 

 series, as represented in the Phoenix beds and the beds of 

 Wallala, Silverado Canon, Point Loma, and Todos Santos 

 Bay, Lower California. 



The fauna of the Chico is characterized in its later por- 

 tions by a large development of gasteropods and lamelli- 

 branchs. It is divisible into two horizons, at least in the 

 Sacramento basin, and perhaps elsewhere. The move- 

 ments that have affected the region are to be inferred from 

 the relations thus recognized. Their general order, par- 

 ticularly in the basin of the Great Valley, has been down- 

 ward from the first, but not continuously so. With the 

 close of the Knoxville epoch, an interval of epeirogenic 

 uplift prevailed, which withdrew a large amount of terri- 

 tory from oceanic submergence, but which in favored 

 places may have caused only a cessation of deposition, as 

 in the Great Valley basin. The extent of this disturbance, 

 and the duration of the interval, may be inferred from the 

 great faunal change which was introduced with the Horse- 

 town epoch. This was the most important disturbance of 



(6) December 3, 1902. 



