THE CHICO-SHASTA FAUNA. 



209 



difficulty was encountered, due to the intermingling of the localities. 

 Chico fossils were found in the vicinity of Ono, on the North fork of 

 Cottonwood creek, and elsewhere, close to the base of the Horsetown 

 beds. Their presence in such positions, associated with well recognized 

 Shasta fossils, cannot be satisfactorily explained by attributing it to the 

 deformation of the strata, in which they are contained. 



A review of the literature, including notes on recent collections con- 

 cerning the faunas of the Chico and Shasta formations, respectively, in 

 northern California, shows that these faunas are much more closely re- 

 lated than formerly supposed. 



Gabb reports* that Ammonites bates hi, Gabb, A. remondii, Gabb, and 

 Ancyloceras (?) lineatus, Gabb, have been found in both the Chico and the 

 Shasta groups. Dr. White f adds, with some doubt, Ammonites stoliczkan us, 

 Gabb. To this small list may now be added the following species : 



Actasonina pupoides, Gabb. 

 Amauropsis oviformis (?) 

 Ammonites hoffmanni (?) il 

 Area breiveriana, 

 1 1 rlium transluc I dam, 

 Cordiera mitrseformis (?) " 

 H< (.mites vancouverensis, 

 Mcekia radiata, 



" sella, 

 Pecten opcrculiformis, u 

 Ringicula varia, 

 Straparollus paucivolus (?) " 

 Trigonia evansana, Meek. 



" tryoniana, Gabb. 



Trigonia leana, 



" equicostata, 

 Pa nopsea concentr let i , 

 Cuculsea truncata, 

 Cardium annulatv. m, 

 Corbula traskii, 

 Mytilus quadratics, 

 Leda translucida, 

 Mcekia navis, 

 Tellina mattheivsonii, 

 Chione varians 

 Mactra ashb urneri, 

 Tellina hoffmanniana, 



Gabb. 



Besides the twenty-five species definitely determined there are six 

 whose identification is doubtful. Of the latter it may be said that, if not 

 identical with the species named, they are most likely closely related. 

 If these identifications are correct there are thirty-one species which con- 

 tinue from the Horsetown beds over into the Chico. Furthermore, in 

 addition to these there are numerous genera common to both series, but 

 not represented, so far as yet known, by determinable common species. 



The intermingling of Shasta and Chico fossils in the same beds may 

 he seen best at Horsetown and Texas springs, J where those noted in the 



*Geol. Survey of California: Paleontology, vol. ii, 18—, pp. 211-213. 



t Bulletin 15, U. S. Geol. Survey, p 19. 



| Texas springs are on the northern side of Clear creek, three mil'-s below Horsetown, Shasta 

 county, California. At these two localities there are not more than 100 feet of Cretaceous rocks 

 exposed, resting directly, with marked unconformity, on fossiliferous Jura-Trias and older rock?. 



