FOSSILS FROM UPPER JURA OF CALIFORNIA. 403 



Copperopolis. is very generally distributed and gives also positive evi- 

 dence that the Gold belt forms of Perlsphinctes belong largely to the group 

 of P. nlternans of the Upper Jura of Russia. 



Gabb's type of Ammonites coif ax l and the positive information it affords 

 that it is a species oi Perlsphinctes, together with the description of Peri- 

 sphinctes muhlbachi, another allied, but new species, from the black slates 

 of the same series of rocks southward, in Eldorado county, and speci- 

 mens of the species mentioned by Whitney * as coming from near Fol- 

 som, Sacramento count}', which is a variety of muhlbachi, all show that 

 the slates of the Gold belt are of Upper Jurassic age. This result is 

 strengthened by the obvious affinities between miihlbachi and the Peri- 

 sphinctes found in the slates of Tuolumne and Calaveras counties to the 

 south of the localities first mentioned. 



FELECYPODA AXD GASTEROPODA. 



The Pelecypoda and Gasteropoda from these localities are too frag- 

 mentar}' to be of much value, except the Amusium aurarium, Meek, (?) 

 which may be identical with ]\[eek's si)ecies, l:)ut it is not perfectly sym- 

 metrical, as in Meek's figure, and some d()u])t is created by this fact. 



The remains of Belemnitinae were found at localities in ^Mariposa 

 county and near Greenwood, in Eldorado county. The forms are closely 

 allied, if not identical, in all the localities explored, but the conditions of 

 these fossils are very unfavorable for exact comparison. They do not 

 help us to determine the age of the rocks, since I am not able to com- 

 pare them clearl}'- with species from other phices. 



A UCELL.E. 



General Remarks. — The remains of Aucelhe are, as a rule, flattened by 

 compression, but the markings and forms of the shells can be studied in 

 detail. There is, of course, considerable danger that one may be some- 

 times representing the results of compression as specific differences, but 

 I know of no way of avoiding this except by the use of large numbers 

 of specimens, and there has been no dearth of materials. The gentlemen 

 who collected them have had the true spirit of good collectors and filled 

 their bags whenever they had an oi)portunity. The following remarks 

 are abstracts of results, which will be given in more detailed descriptions 

 of the species. 



Aucella erringtoni. — Amelia errlngtoni, Meek, var. arcicata, was found at 

 three places, on south bank of Tuolumne river at Moffats bridge, on 

 Stanislaus river opposite mouth of Bear creek, and six miles from Cop- 

 peropolis on road to Sonora and grade to Angels creek. 



* Auriferous Gravels, p. 37. 

 LVII— Bull, Geol. Soc. Am., Vol. 5, 1893. 



