150 University of California Publications in Geology L VoL - 9 



Desmoceras sugatum (Forbes) 

 Lytoceras jacksonense F. M. Anderson 

 Nautilus texanus Schumard 

 Placenticeras californicum F. M. An- 

 derson 



Placenticeras pacificum J. P. Smith 

 Sehloenbachia knighteni Anderson 

 Terebratula abesa Gabb 



The relationships of the above defined zones are shown in summary 

 in Table II. 



TABLE II 



Actaeonella 

 oviformis 

 zone 



Number of forms 65 



Number of determined species .... 47 

 Number of determined species ap- 

 pearing in the Actaeonella ovi- 

 formis zone 47 



Number of determined species ap- 

 pearing in the Turritella pes- 

 caderoensis zone. Deep water 



phase 11 



Number of determined species ap- 

 pearing in the Turritella pes- 

 caderoensis zone. Shallow 



water phase 18 



Number of species appearing in 



the Tellina ooides zone 4 



Turritella pesca- 

 deroensis zone 



Deep 

 water 

 phase 



25 



16 



11 



16 



13 



Shallow 

 water 

 phase 

 41 



13 



28 



12 



Tellina 

 ooides 

 zone 



26 



18 



12 



18 



Chico 

 Creek 

 fauna 



79 

 79 



12 



16 



17 



RELATION TO OTHER CRETACEOUS FAUNAS OF CALIFORNIA 



Anderson recognized the Chico affinities of the fauna obtained in 

 Silverado Canon on the western slope of the Santa Ana Mountains, 

 but more recent collecting has revealed a large number of species as yet 

 unknown from the typical Chico of northern California. The majority 

 of the forms peculiar to the southern fauna occur in the lowermost 

 beds of that region, suggesting that this stage represents a lower 

 horizon than that known at Chico Creek. This raises a question as to 

 the definition of the beds of the Chico and also as to reasons for the 

 difference between the faunas of the Chico and the Santa Ana 

 Mountains. 



In considering the relation between the faunal stages of the typical 

 Chico and the Cretaceous of the Santa Ana Mountains it is necessary 

 to review briefly the relationships of the Chico fauna of Shasta and 

 Tehama counties to that of the underlying Horsetown. 



