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



1891. G. F. Becker^ concludes that the Mariposa slates are Gault. 

 H. W. Fah'banks f says that the evidence is in favor of the Jurassic age 

 of the Auriferous slates and the limestones associated with them. 



1892. James E. Mills J gives about the same stratigraphy of the 

 Sierra Nevada rocks as that given by Whitney,§ and refers one portion 

 of the series to pre-Mesozoic time ; another to Lower Mesozoic, on the 

 evidence of the occurrence of Pentacrinus and Ammonites colfaxi, both sup- 

 posed to be indicative of Jurassic age, and a third portion he refers to 

 Upper Mesozoic from supposed equivalence with the Mariposa slates. 



1893. G. F. Becker II divides the Auriferous slates series into the Cal- 

 averas formation and the Mariposa formation. The Calaveras formation 

 is to include all the Paleozoic deposits of the Sierra Nevada, except the 

 Silurian, described by J. S. Diller, from Plumas county,^ and afterwards 

 named the Grizzly formation.^* 



The Mariposa formation makes up the upper division of the Auriferous 

 series. None of the supposed Triassic of the Sierra Nevada comes within 

 this sheet, but similar ones at the northern end of those mountains have 

 been named the Cedar ff formation. 



H. W. Turner JJ gives several localities for Carboniferous and Mesozoic 

 fossils in the Auriferous slates series, but does not give any exact horizon. 



Determined Horizons and v\^ell-known Fossil Localities. 



In presenting the results of the investigations it seemed best to the 

 writer to give in tabular form all the known localities for fossils in the 

 metamorphic series, and then to follow with a discussion of those occur- 

 rences about which new information could be added. 



Review of recent Discoveries and Determinations of Fossils. 



ca rb on i per ous loca li ties. 



Longville, Plumas County. — This localit}^, which is near the town of 

 Longville, was first mentioned by J. S^ Diller,§§ who found there Litho- 

 strotion whitneyi, Meek, Lophophyllum proliferum (?) and a Spirifer (?). In 

 a later paper |||| he refers to this locality again, and quotes C. D. Walcott 



*BulI. Geol. Soc. Am., vol. 2, pp. 189-208. 



t Am. Geologist, vol. vii, p. 219. 



JBulI. Geol. Soe. Am.„vol. 3, pp. 413-414. 



§ Auriferous Gravels, pp. 44-49. 



II Geological Atlas, U. S. Geol. Survey, Sacramento Sheet. 



T[Bull. Geol. Soe. Am., vol. 3, 1892, p. 376. 



** Geological Atlas, U. S. Geol. Survey, Lassen Peak Sheet, 1892, J. S. Diller. 



ft Geological Atlas, U. S. Geol. Survey, Lassen Peak Sheet, 1892, J. S. Diller. 



II Am. Geologist, vol. xi, pp. 307-324. < 

 ggBull. 33, U. S. Geol. Survey, p. 11. 



III Bull. Geol. Soc. Am., vol. 3, p. 375. 



