^50 WILLIS T. LEE 



and general aspect the bones are similar to the Dinosaurian 

 remains of the Atlantosaurus Beds of central Colorado and 

 Wyoming - . 1 



That portion of the general section for the Rocky Mountain 

 region which is useful for present comparison is as follows: The 

 Red Beds formation (the so-called Jura-Trias) is overlain by the 

 Morrison formation, or Atlantosaurus Beds. The line of demarca- 

 tion is drawn at the top of the gypsum beds which occur in several 

 localities along the mountains at the summit of the Red Beds. 

 The gypsum is regarded as marking the closing stage of the Red 

 Beds period. The Morrison formation, which averages about 

 200 feet in thickness, is composed principally of variegated 

 shales. These contain sandstones and impure limestones, the 

 thickness and relative position of which vary from place to place, 

 or may be entirely wanting. It is this formation which is noted 

 for its huge Dinosaurs. Above the Morrison occurs the Dakota 

 sandstone. It should be borne in mind that only the middle 

 one of these three formations, the Morrison, contains Dinosaurian 

 remains. 



Since the vertebrate fossils of southeastern Colorado have 

 not been studied, and since they are the only known fossils from 

 the shale formation of that region, we must resort to other 

 means of determining the age of the shales, and these will be 

 chiefly stratigraphical and lithological, to which may be added 

 such general paleontological evidence as may be drawn from 

 unidentified bones. 



a. As stated in a previous paragraph, the upper sandstone of 

 the region in question was traced from a known area, and there 

 can be little doubt, therefore, that it is Dakota. The Red Beds 

 are in structure, color, and general aspect similar to the Red 

 Beds of the mountain region, seventy-five miles to the west. 

 They differ only in being composed of finer material and in being 

 massive near the top instead of evenly stratified, as is often the 



'Since writing this article my companion, Mr. T. A. Pierce, has again visited the 

 bone beds and found a number of new localities where bones occur in considerable 

 numbers. The width of the territory in which these remains are found and their 

 number indicate that this region would yield rich rewards to the bone hunter. 



