SOME EARLY MAMMALS 259 
matrix that the brain-cavity and the openings leading from it 
could be worked out without difficulty. 
It is about forty-one years since the wonderful forms of life 
sealed up within these Eocene lake-deposits first became known 
to science. Long before then, however, the wandering Indian 
had been accustomed to seeing strange-looking skulls and 
skeletons that peeped out upon him from the sides of caiions and 
hills, as the rocks that enclosed them crumbled away under the 
influence of atmospheric agents of change—the ceaseless working 
of wind, rain, heat, and cold. To his untrained mind no other 
explanation suggested itself than the idea that these were the 
bones of his ancestors, which it would be highly impious to 
disturb. Reguiescant in pace! So he left them in peace. 
Perhaps he believed in a former race of human giants; if so, 
these would be their bones. Long before Professor Marsh’s 
expeditions, the earliest squatters, trappers, and others used to 
bring back news of marvellous monsters grinning from the ledges 
of rock beneath which they camped. At last these tales attracted 
the notice of some enthusiastic naturalists in the eastern States. 
Professor Leidy obtained a number of bones, from which he was 
able to bring to light an extinct creature at that time unknown 
to science, namely, the Uintatherium. Professor Cope also 
described some extinct animals disinterred by himself from the 
same region. 
But our knowledge of the Dinocerata is chiefly due to Professor 
Marsh, who has despatched one expedition after another, and 
who, after many years of laborious research both in the western 
deserts and in his wonderful collection at Yale College, has 
published a splendid monograph on the subject. No trouble 
and no expense have been spared in order to obtain material for 
this great work, and all geologists must feel grateful to Professor 
