132 ENVIRONMENT OF VERTEBRATE LIFE, ETC. 



central granite mass of Idaho. On page 194 Lindgren speaks of these rocks 

 as follows: 



"The rocks of the series consist of a comparatively small amount of heavy- 

 bedded gray limestones and a large mass of quartzitic sandstones of red, gray, or 

 brown color. Very frequently these are more or less calcareous. Black shales, 

 usually calcareous and frequently banded, gray and black, are also abundant, 

 and contain most of the veins in the district. Occasionally slaty rocks are met 

 with, showing the effects of great compression in slaty cleavage, frequently in 

 two directions." 



A number of casts of fossils were found in a hard, grayish brown, partly 

 calcareous quartzite which have been identified by Schuchert as Myalina 

 (two species), Schizodus, Allorisma, Scaphiocrinus or Graphiocrinus, and 

 Fusulina (?). Dr. Schuchert^ says concerning this fauna: 



"The identification of Fusulina is doubtful, since only two large cross-sections 

 are shown embedded in the rock. They are pseudomorphs in calcite, and preserve 

 only the spiral layers of growth. If Fusulina is present the horizon is upper 

 Carboniferous. The presence of Scaphiocrinus or Graphiocrinus often indicates 

 a rather lower horizon — lower Carboniferous — though Graphiocrinus is also found 

 in the upper Carboniferous. The pelecypods indicate no special horizon in the 

 Carboniferous. For the present I am inclined to view these fossils as probably 

 upper Carboniferous." 



In northwestern Wyoming and southwestern and western Montana, 

 the horizon of the Weber quartzite becomes somewhat mixed, limestone, 

 sandstone, and shale layers occurring at frequent levels and sometimes 

 dominating the quartzite. The deposits in this region are called Quadrant 

 quartzite, and there has been considerable difference of opinion as to its 

 exact age and correlation with other beds, but there can be little doubt that 

 the Quadrant quartzite, or a part of it, is the equivalent of the Weber 

 quartzite and that its deposition was due to similar conditions. 



In the Yellowstone National Park,^ the Quadrant quartzite — 



"consists of white, yellowish and occasionally pink beds of quartzite, with 

 intercalated beds of drab saccharoidal limestones. The quartzite is generally 

 compact, occurs in beds from 4 to 25 feet in thickness, and weathers in massive 

 blocks. More rarely it breaks into small fragments that form debris slopes, as 

 seen in the Teton Range. The total thickness averages 400 feet in the Gallatin 

 Range. In the southwest corner of the park it is far less prominent than in the 

 Gallatin, but its resistance to weathering makes it easily recognizable, out- 

 cropping beneath the soft red clays of the Juratrias. * * *" 



{i) Conditions in Montana. — ^At Three Forks, Montana, the quartzite of 

 this horizon is less dominant, except at the top. In the description of this 

 area by Peale^ the following account is given : 



^ Schuchert, in Lindgren, 20th Ann. Rept. U. S. Geol. Sur., p. 90. 



^ Yellowstone National Park Folio, No. 30, U. S. Geological Survey, p. 5, 1896. 



^ Peale, A. C, Three Forks, Montana, Folio No. 24, U. S. Geological Survey, p. 2, 1896. 



