358 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



The Upper Trias. 



The Upj^er Trias of Pliinias County, Califo7'nia. The 

 Whitney Geological Survey of California first discovered 

 fossils characteristic of the Upper Trias in some shales 

 near Robinson's Ranch in Genesee Valley on Indian 

 Creek, Plumas County. Only the Upper Trias is repre- 

 sented in the section at that locality, the shales and lime- 

 stones resting unconformably on the Carboniferous. Only 

 a very few fossils were found there, but Psetido?nonotis stib- 

 circiilaris Gabb was enough to determine the age of the 

 beds. This along with Ammonites ramsaueri Gabb (not 

 Hauer) and a few other molluscs, was described by W. M. 

 Gabb in Vol. I, Palaeontology of California, in which also 

 the first description of the Middle Trias of Nevada was 

 published. 



Many years later Mr. J. S. Diller and Professor Alpheus 

 Hyatt visited the Trias of Plumas County, and undertook 

 a revision of the work of Gabb. They found numerous 

 fossils in the limestones as well as in the slates, and proved 

 the occurrence in California of a fauna equivalent to the 

 classic Hallstatt fauna of the Alps. The general section of 

 the Trias of Genesee Valley as worked out by Diller (7) 

 and Hyatt (13) is as follows: 



1. Hosselkus limestofie, with Tropites conf. subbullatus, Jiiva- 140 ft. 



vites, Badiotitesf, Arcestes, Atractites, 



2. Halobia slates, with Halobia conf. superba, H. conf. rugosa, [about 100 ft.] 



Tropites conf. snbbuttatus, Arcestes, Atractites, 



3. Swearinger slates, 200 ft. 



Rhabdoceras bed, with Rhabdoceras, Atractites, Halorites, 



Arcestes, and numerous pelecypods. 

 Daonella bed, with Daonella, Pseudomonotis, and numerous 



pelecypods. 

 Pseudomonotis bed, with Pseudomonotis subcircularis, and 



other pelecypods. 



The Swearinger slates were supposed to underlie the 

 Halobia slates, but the strata are much faulted and the 

 sequence obscure. Hyatt (13) states that " above the 

 Rhabdoceras bed lie unfossiliferous quartzites, but to the 

 westward, near the top of the Carboniferous spur (so- 



