II 



Several skeletons of animals have been found in a standing position, with 

 their legs slightly stretched out. They were probably mired, and, being unable 

 to extricate themselves, died in an erect position. This fact affords evidence 

 that extensive swamps surrounded the borders of the lake. 



The snow-water and the spring rains wear deep guileys through the lines of 

 cliffs, and wash down fragments of bones into the dried-up water-courses. 

 These pieces can generally be traced up to the spot from which they came, and 

 the rest of the skeleton can so be secured. 



The fossils found in the eocene of Wyoming are entirely petrified, presenting 

 a darker appearance than their matrix ; but loose bones washed out, and sub- 

 jected to the influence of the sun and rain, often become bleached so as to re- 

 semble in color modern bones. 



The state of preservation of the fossils differs according to the matrix in 

 which they are found. Generally speaking, the remains found in the lower 

 lines of buttes have been considerably distorted by pressure ; while those from 

 the highest line have suffered very little from this cause. 



