WEST HUMBOLDT RANGE. 723 



the presence of finely- disseminated carbon, and the ti-ansition from the 

 higlily-metamorphosed to the unaltered rocks place the sedimentary origin 

 of these porphyroids beyond question. 



Directly overlying the clays and slates of the Koipato series occurs 

 the lowest limestone belt of the Star Peak Triassic. This limestone varies 

 much in color near the bottom, consisting of dark, almost black, beds, pass- 

 ing up into grays and blues, and, north of Star Canon, is much stained 

 with red oxide of iron, at the same time showing a great amount of Assuring 

 with the strike and dip. Organic matter appears to be present throughout 

 the greater part of the series, and the black color in many of the beds is 

 evidently due to the presence of carbon. Two analyses of limestone from 

 this series, taken from widely-separated localities, have been made by Mr. 

 B. E. Brewster ; No. 1 is from the lower beds in Star Canon, a fine-grained 

 black rock; No. 2 is from the ridge dividing Buena Vista from Cottonwood 

 Canon, and is a more crystalline lighter-colored variety. 



1. 2. 



Alumina and ferric oxide - .. 0.188 0.256 



Lime 51.689 52.165 



Magnesia 1.036 2.470 



Carbonic acid 41.752 43.704 



Phosphoric acid trace trace 



Organic matter 0.809 trace 



Insoluble residue 4.526 1.613 



100.000 100.208 



The lower beds of the series contain a great number of Triassic fossils 

 characteristic of the Star Peak formation, which is undoubtedly the equiv- 

 alent of the Alpine Triassic, not only the genera, but many of the species, 

 being either identical with, or closely related to, well-recognized forms 

 described from the St. Cassian and Hallstadt limestone beds of the Alps. 

 Although the same species may be found scattered through the entire belt, 

 there appears to be near the upper limits a second zone, rich in fossils, 

 which carries with the other forms ribs of Vertehrata, too poor, however, for 

 specific determination. 



