1916] 



Packard: Cretaceous of Santa Ana Mountains 



153 



base of these beds just below the mouth of Hulert Creek might well 

 be taken as the base of the Chico group. This apparently agrees with 

 White's original idea of the location of the base of that group judging 

 from the fauna obtained above and below the horizon. 



The differences of opinion as to the location of the base of the 

 Chico group tend to substantiate the view of Diller and Stanton 23 

 regarding- the stratigraphic continuity of the Shasta-Chico series, and 

 show the necessity of detailed faunal studies within this region before 

 the Horsetown and Chico faunas can be clearly defined. Regardless 

 of the final decision on this point, it seems advisable for the purposes 

 of this paper to consider the fauna obtained at Horsetown and its 

 correlative on Hulen Creek as uppermost Horsetown. 



In compiling a list of Horsetown species for comparison with the 

 fauna from the Santa Ana Mountains only those species have been 

 included that are known to have come from the Horsetown beds as 

 defined above. Such a procedure considerably reduces the published 

 Horsetown fauna. 



A comparison of such a list with the faunal list from the Santa 

 Ana Mountains reveals the following species in common: Cucullaea 

 truncata Gabb, Nemoclon vancouverensis (Meek), Trigonia evansana 

 Meek, Peeten operculiformis Gabb. These species have a long range, 

 occurring in the Chico of Chico Creek. From this very small repre- 

 sentation of common forms it would appear that the latter fauna is 

 not the equivalent of the Horsetown as it is now imperfectly known. 



The term Chico was first used by Gabb in a paper read before the 

 National Academy of Sciences in August, 1868. 24 The type locality 

 as designated by Gabb in the Palaeontology of California 2 * is very 

 indefinite, including beds most extensively represented in Shasta and 

 Butte counties, California. The group was named for Chico Creek, 

 along which a number of fossiliferous localities occurred. 



Recent studies made by C. K. Studley show that the three fossilifer- 

 ous localities on Chico Creek contain faunas so closely related that they 

 may be considered as a unit. - ( ' The faunas already published by 

 Gabb 27 and Turner 28 have been greatly increased through the eollee- 



23 Op. at., p. 464. 



2-i Gabb, W. M., Palaeontology of California, vol. 2, p. xii, 1869. 

 - x < Op. cit., p. xiii-xiv. 



-'< Studley, C. K., MS thesis, University of California, 1914. 

 " Gabb, W. M., Palaeontology of California, vols. 1 and 2, 1864-1899. 

 28 Turner, H. W., The rocks of the Sierra Nevada, Fourteenth Annual Report 

 U. S. Geol. Surv., pt. 2, p. 460, 1892-1893. 



