460 DILLER AND STANTON — THE SHASTA-CHICO SERIES. 



Colorado, in which there are several species of both Gasteropoda and 

 Pelecypoda that are related to Chico as well as to Ripley species. These 

 are associated with Inoceramus labiatus in beds that may be correlated 

 with the Turonian, and they are mentioned here simply to show that 

 many of the Chico t^^pes which have been compared with species in 

 the Ripley and Montana formations (Senonian) are also represented by 

 related forms in earlier deposits. 



The direct evidence from the Chico fossils cannot be presented fully 

 at this time, as that would require the review of the entire fauna and the 

 description of a number of new species obtained in recent collections. 

 It is a significant fact that the most abundant Ammonites of the Chico 

 belong to the genus Schloenbachia (in the broad sense in which the name 

 is used in Europe). Ammonites chicoensis, Am.monites tehamaensis and two 

 undescribed species belong here and these are all found in the upper 

 beds of the Chico. In other American cretaceous areas this genus does 

 not pass above the top of the Colorado formation and its equivalents, and 

 in Europe it seems not to occur above the " Emscher Mergel " or lowest 

 Senonian. Ammonites titrneri which was found near Mount Diablo asso- 

 ciated with Anchura calif ornica and other lower Chico species is an Acan- 

 thoceras closely related to European species that occur in the Cenoma- 

 nian. The other Ammonites known from these beds do not resemble 

 those characteristic of the latest Cretaceous. The two abundant species 

 of Trigonia, T. evansana and T. leana likewise have their nearest relatives 

 in the lower part of the Upper Cretaceous of Europe. 



The occurrence of Inoceramus labiatus in the upper shales (division 

 A) of Queen Charlotte islands is also a suggestive fact in the same direc- 

 tion when considered in connection with the close relationship between 

 the Shasta and the Chico, and consequently between the Queen Char- 

 lotte " Lower Shales " and the Chico. The equivalent of the Chico on 

 Vancouver island has yielded a considerable flora which Sir William 

 Dawson^ assigns to the older part of the Upper Cretaceous, though he 

 regards it as later than the Dakota. He states that " there would seem 

 to have been a geographical separation between the Pacific coast and 

 the plains, as the latter have not yet yielded anything equivalent to the 

 Vancouver flora.'' 



In Oregon the Tejon appears to overlie unconforniably the Shasta - 

 Chico series under such conditions as to suggest that a considerable 

 period of erosion occurred between the uplifting of that series and the 

 deposition of the Tejon. The faunas of the Chico and the Tejon as de- 

 veloped there are entirely distinct. The stratigraphic and faunal evi- 

 dence tends to show that in the regions in which we have studied it the 



* Fossil Floras and Climate. Nature, vol. 47, p. .557, April, isn.'l 



