" To those interested, it may be well to dwell at some length upon the fossil fields, 

 their nature, and just what one may expect to find in each. 



"While Paleozoic rocks are found flanking every mountain range, they are in no way 

 comparable with the vast beds of sediment found along the Appalachian Mountains. These 

 are Cambrian, Ordovician, Silurian, and Carboniferous; but, taken as a whole, they are seldom 

 over 3,000 feet thick. The fossils the)" contain are only partially known, and on comparison 

 with similar groups in the east, they are not rich in fossil life. Not over one hundred species 

 have been reported from them. 



" The Mesozoic of the west, on the other hand, corresponds in thickness and importance 

 to the Paleozoic of the east, and in its maximum development is nearly 25,000 feet thick. 

 It also covers vast areas along the mountains and in the valleys — stretches half way across 

 the State, and in one place is over one hundred miles in breadth. These rocks are made up 

 of three distinct periods — the Triassic, Jurassic, and the Cretaceous. The Triassic or ' red 

 beds,' as they are usually called, are chiefly bright red sandstone and gypsum, and vary 

 from 800 to 1,200 feet in thickness. So far as known they do not contain any fossil lite. 



" The Jurassic rocks, the second period, are wonderfully rich in reptilian remains, and 

 contain as well many mammals and fishes. The University of Wyoming commenced col- 

 lecting the reptilian fossils only three years ago, and now has partial skeletons of over one 

 hundred animals. The most of these belong to theso-called Dinosaurs, the largest land animals 

 that ever lived, and so large in fact that when one describes them the majority of people 

 consider the description to be a ' western yarn ' without foundation. Nevertheless the 

 scientific articles published along this line can be considered correct. The University of 

 Wyoming's collection can be summed up as follows: Ten Ichthyosaurs {Baptauodou discus. 



2\ 



