178 QUICKSILVER DEPOSITS OF THE PACIFIC SLOPE. 



Pence'* ranch, in Bntte County, and inferred from similarity of position 

 and lithological character that other rocks on the western flank of the 

 SieiTa may also be of this age. No Carboniferous fossils are known to 

 occur in the Coast Ranges. 



Fossiliferous beds were found by Professor Whitney's pai-ty at Genes- 

 see Valley, in Plumas County, which Mr. Meek determined as Triassic. 

 The material upon which this determination rests appears, however, to be 

 somewhat meager and unsatisfactory. A similar fauna has been found at 

 a few points in Nevada,' but not elsewhere in California. Near the south- 

 ern end of the gold belt of California fossils were found on the Mariposa 

 estate in 1864" They were figured and described by Meek.' The mosi 

 important shell he determined as Amelia Erringtonii, the specific name being 

 given in honor of a resident who drew attention to the occurrence of the 

 fossil. Meek 'observes : '' 



As tbis genus is, so far as kuowii, eutirely coufliieil to the Jurassic rocks, wliik 

 au AmHssiuiii like shell from the same slates is closely allieil to a Jurassic species, aiui 

 the geiuis Ihlcmnites is not generally regarded as dating back beyond Ihe commence 

 ment of the Jurassic period, I can scarcely entertain a doubt that these gold-bearing 

 slates really belong to that epoch, and probably to some of its lower members, at whicJi 

 horizon most of the known European species of Aiioel la are said to occur. 



The same species of Aucella was foinid by Professor Whitne}''s party, 

 after the publication of Meek's determination, at a number of localities on 

 the gold belt, and ammonites were also discovered. It will be observed 

 that Meek laid the chief weight in his determination of the age of these 

 beds on the occurrence oi Aucella. 



Previous to the discovery of the fo.ssil fiiuna of the Maripo.sa estate 

 fossils had been found at many points on the Coast Ranges and along the 

 foot-hills of the Sierra, which were described by Mr. Gabb as Cretaceous.^ 

 Many more were added later, and Mi*. Gabb ultimately divided the Cr -ta- 

 ceous of California into the Shasta, Chico, Martinez, and Tejon groups, the 

 last being tlie highest. 



>Kiug: U. S. Geol. Expl. 40th Parallel, vol. 1, Systematic Geology. 



*Thc honor of the first discovery of these fossils w.is somewliat xvannlj coutested. See Whituey's 

 Auriforons Gravels and Proc. California Acad. Nat. Sei. ; also, Mr. Clareuce King's Mountaineering in 

 Ihe Sierras. 



' Geol. Survey California, Geology, vol. 1, p. 477. 



1 Ibid., p. 478. 



■''Genl. Survey Califorui i, P.iKooutology, vol. I. 



