278 
POPULAR SCIENCE REVIEW. 
year commenced the explorations in the vicinity of Fort 
Bridger, a military post situated in the south-west corner of 
Wyoming Territory, which have yielded such an abundant 
harvest, and the locality of which is thus graphically described 
by Professor Leidy : — 
44 Fort Bridger occupies a situation in the midst of a wide 
plain, at the base of the Uintah Mountains, and at an altitude 
of nearly seven thousand feet above the ocean level. The neigh- 
bouring country, extending from the Uintah and Wahsatch 
Mountains on the south and west to the Wind Biver Bange on 
the north-east, at the close of the Cretaceous epoch, appears 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 vegetation covered the country, in strange contrast to 
its present almost lifeless and desert condition. 
44 The country appears to have undergone slow and gradual 
elevation ; and the great Uintah Lake, as we may designate it, 
was emptied, apparently in successive portions, and after long 
intervals, until finally it was drained to the bottom. The 
ancient lake-deposits now form the basis of the country, and 
appear as extensive plains, which have been subjected to a great 
amount of erosion, resulting in the production of deep valleys 
and wide basins, traversed by Green Biver and its tributaries, 
which have their sources in the mountain boundaries. From 
the valley of the Green Biver the flat-topped hills rise in 
succession, as a series of broad table-lands or terraces, extending 
to the flanks of the surrounding mountains. 
44 The fossils which form the subjects of our communication 
for the most part were derived from the more superficial 
deposits of the great Uintah basin, which Professor Hayden has 
distinguished as the Bridger group of beds. These compose 
the terraces or table-lands in the neighbourhood of Fort Bridger, 
and consist of nearly horizontal strata of variously-coloured 
indurated clays and sandstones. As the beds wear, through 
atmospheric agencies, on the naked declivities of the flat- 
topped hills, the fossils become exposed to view, and tumble 
down to the base of the hills among the crumbling debris of 
the beds.” 
The immense length of time that this ancient lake has existed 
may be inferred from the fact that the mud or sand deposited 
in it has accumulated to more than a mile of vertical thickness. 
It is from this and from neighbouring localities systematic- 
ally explored only during the last four or five years, both by 
the Government surveys and by expeditions organised for the 
purpose from Yale College, that most of the remarkable animals 
