Description of part of Wyoming Territory. 2G9 



they form broad, lenticular sheets. It seems to me that we have some 

 evidence that the local accumulation of these beds of sand produced 

 local displacement of th'e mud on -which they were deposited, just as 

 they do at the mouth of the Mississippi, where the displacement results 

 in the formation of "mud-lumps." But the theory of Professor An- 

 drews seems to me not simply untrue, but as calculated to do positive 

 and practical harm, since teaching that a discrepancy of interval 

 argues a want of identity in coal-seams, it tends to multiply their 

 numl)er and produce confusion in their classification. 



Interesting Description of a part of Wi/oming Territory , from the intro- 

 duction to "Extinct Vertebrate Fauna of the Bridger Fvrmhtionf 

 by Prof. Joseph Leidy. 



Fort Bridger occupies a position in the midst of a wide plain, at the 

 base of the Uintah mountains, and at an altitude of nearly 7,000 feet 

 above the ocean level.- The neighboring country, extending from the 

 Uintah and ^Yahsatch mountains on the south and west to the Wind 

 river range on the northeast, at the close of the cretaceous epoch, ap- 

 pears to have been occupied by a vast fresh water lake. Abundance 

 of evidence is found to prove that the region was then inhabited by 

 animals as numerous and varied as those of any other fauna, recent or 

 extinct, in other parts of the world. Then, too, a rich tropical vege- 

 tation covered the country, in strange contrast to its present almost 

 lifeless and desert condition. 



The country fippears to have undergone slow and gradual elevation, 

 and the great Uintah lake, as we may designate it, was emptied, ap- 

 parently in successive portions and after long intervals, until finally it 

 w\as drained to the bottom. 



Tlie ancient lake deposits now form the basis of the country, and 

 appear as extensive plains, which have been sulijected to a great amount 

 of erosion, resulting in the production of deep valleys and wide basins, 

 traversed by Green river and its tributaries, which have their sources 

 in the mountain boundaries. From the valley of Green river the flat 

 topped hills rise in succession asaseries of broad table lands or terraces 

 extending to the flanks of the surrounding mountains. 



The snows of the Uintah, Wahsatch, and other mountain ranges are 

 a never-failing source to the principal streams ; but many of the lesser 

 Ijranches, dependent for their supply on the accumulated snows of 

 winter in ravines of the lower hills and plains, completely dry up as 



