40 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 30 Ser. 



and especially the two species of Acanthoceras, the Lytoc- 

 eras species, and others may be taken as evidence of 

 a rather low position in the Chico. Moreover, beds of the 

 same or of a little later age at Jacksonville, only a few 

 miles to the west, contain Lower Chico forms, such as 

 Trigonia cequicostata, T. leana, Pecten operctilifortms,'e\.c., 

 which have not been found above the Lower Chico. Nor 

 is there a single species among this collection that is char- 

 acteristic of even the uppermost Horsetown beds. 



The horizon of the Phoenix beds is almost identical with 

 that of Cottonwood Creek and Shasta Valley, in Siskiyou 

 County. Near the town of Hornbrook (Henley) the Cre- 

 taceous beds have a thickness approaching 2,500 feet, the 

 lower two-thirds of which is fossiliferous. There are two 

 well marked horizons, the lower one containing an abund- 

 ance of trigonias and other bivalves and gasteropods, and the 

 upper one containing a comparatively large number of ceph- 

 alopods, among which are two species of Placenticeras, two of 

 Desmoceras, a Pachydiscns, and two species of PhyUocei'as. 

 On Willow Creek, a few miles south of the Klamath River, 

 and in the strike of the Henley beds, the same horizons occur 

 in the same relation. Here the upper zone contains also 

 Pachydiscns newberryanus, Desmoceras hoffmanni, Prionotro- 

 pts crenulatuni, Scaphites condoni, Hainites artnattini, Des- 

 moceras sp., and many others of a Lower Chico aspect. 



The Horsetown Epoch. 



An examination of the Horsetown fauna shows it to con- 

 sist in large part of abundant species of cephalopods, espec- 

 ially of the genera Desmoceras and Lytoceras ; their relatives, 

 Hoflites and Acanthoceras are also common; and there 

 are, perhaps, three or four species of Phylloceras, one or 

 two of Olcostephamis, at least two species of Nautilus, and 

 two of Belemnites. One-half of the entire fauna of the 

 Horsetown belongs to the class of cephalopods, and this pro- 

 portion seems to be fairly constant throughout. Probably 

 when the fauna of the Horsetown strata becomes more per- 

 fectly known, the proportion of cephalopods among the 



