250 J. p. SMITH — AGE OF THE AURIFEROUS SLATES. 



the Trias of this region. The writer visited this locality in October, 1893, 

 and found Pentacrinus, Encrinus (?) Spiriferina and Attractites. The evi- 

 dence is therefore sufficient to place these rocks in the upper part of the 

 Trias, probably Karnic. 



Rush Creek Mine, Plumas County. — J. S. Diller* includes this limestone 

 in his Cedar formation, basing his conclusions on the Triassic fossils he 

 found there. 



James E. Mills f published the first notice of the occurrence of Pen- 

 tacrinus in these beds, and called them Jurassic or later, upon the opin- 

 ion of Dr Charles Wachsmuth, who thought that this type of crinoids 

 did not antedate the Jurassic. Pentacrinus, however, is well known to 

 occur in the Trias in Europe, and has been found in rocks of that age in 

 three other places in California, associated, as in this case, with un- 

 doubted Triassic fossils. 



In October, 1893, the writer visited this locality in company with 

 Mr Mills, and found numerous characteristic Upper Triassic fossils of 

 the horizon of the Hosselkus limestone. At the top of the series was 

 seen diabase-tuff with pebbles of granitoid rock. Below this were several 

 feet of shaly siliceous limestone with pebbles of phthanite and granitoid 

 rock, Pentacrinus, Cidaris, Spiriferina and an undescribed species of Trop- 

 ites, identical with specimens collected in Shasta county. Below the 

 Pentacrinus limestone are seen dark, very thin bedded shales, which, 

 where not too much altered, showed Attractites and Halohia superba (?), 

 Daonella (?), and Avicula. This fauna is identical with that described 

 by A. Hyatt % from the Genesee valley, and also with that found by 

 H. W. Fairbanks between Squaw creek and Pit river, Shasta county. 

 It is of Karnic age of the Upper Trias, and the stratigraphy agrees with 

 that of Plumas and Shasta counties, where the Halobia slates underlie 

 the Hosselkus limestone. 



Below the Halobia slates are about 1,500 feet of siliceous, dark shales 

 and tuffs, very much like the underlying shales of Shasta county, where 

 they are known from fossils to be in part of Triassic age, probably Noric. 

 In the Rush creek region no fossils were found in them. Next to the 

 shales is a large mass of serpentine, but it is not known whether it is 

 conformable or not, or whether it underlies them. 



JURASSIC LOCALITIES AND FA UNA. 



Texas Ranch, Calaveras County. — This locality, which is on the ranch 

 of Charles Grossman (" Texas Charlie "), is in the valley of Angels creek, 



* Geol. Atlas, U. S. Geol. Survey, Lassen Peak sheet, 1892, top of third column of descriptive text. 



tBull. Geol. Soc. Am., vol. 3, p. 428. 



X Bull. Geol. Soc. Am., vol. 3, pp. 395-412. 



