SOME AMERICAN MONSTERS. x 
never before been explored. It was here, also, that he found the 
wonderful series of fossil horses by means of which he has been 
able to prove that our modern horse is descended from a small 
quadruped with five toes, and to show the different stages in its 
evolution. Here, also, were found old-fashioned types of car- 
nivorous quadrupeds, of rodents, and of insectivorous creatures. 
But reptiles as well as quadrupeds flourished on the borders 
of the old lake, for the remains were found of crocodiles, 
tortoises, lizards, and serpents; its waters, too, were well stocked 
with fish. 
Everything here testifies to a long continuance of those con- 
ditions under which plant and animal life can flourish, namely, a 
warm climate, plenty of food, and freedom from those physical 
changes which, by altering the geographical features of a country, 
bring so many important consequences in their train, The 
geological record tells us that this happy state of things lasted 
all through the Eocene period, and until the fresh-water lakes 
had at last been drained away by their outflowing rivers. 
In October, 1870, a later Eocene lake-basin was discovered by 
the same exploring party, and this Professor Marsh calls the 
Uinta basin, because it was situated south of the Uinta Moun- 
tains. “In the attempt to explore it,” he says, “our party 
endured much hardship, and also were exposed to serious danger, 
since we had only a small escort of United States soldiers, and 
the region visited was one of the favourite resorts of the Uinta-Utes. 
These Indians were then, many of them, insolent and aggressive, 
and since have been openly hostile, at one time massacring a large 
body of Government troops sent against them. Two subsequent 
attempts . . . to explore this region met with little success.” 
This lower lake was of later (or upper) Eocene age, and the 
extinct animals preserved in its ancient bed appear to resemble 
more nearly those of the famous Paris basin, referred to in the 
beginning of this chapter, than any yet discovered in America. 
But the basin north of the Uinta Mountains, where alone the 
