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42 ©  STRATIGRAPHICAL GEOLOGY.  [Boox VL. _ 
It is from the thick Eocene lacustrine formations of the western 
Territories of the United States that the most important additions 
to our knowledge of the animals of early Tertiary time have recently 
been made, thanks to the admirable and untiring labours first of 
Leidy, and subsequently of Marsh at N ewieney and vic at 

Fic. 404.—Eocrnr FIsues. 
a, Lamna elegans (Ag.) tooth of (3); b, Otodus obliquus (Ag.), tooth of (). 
Philadelphia. The herbivorous ungulata appear to have formed a 
chief element in that western fauna. “They included some of the oldest 
known ancestors of the horse, with four-toed feet, and even in one 
form (Hohippus) with rudiments of a fifth toe ; also various hog-like 
animals (Hohyus, Parahyus). Some of the most peculiar forms were 

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Fic. 405.—PALMOTHERIUM MAGNUM (CUV.). 
those of the type termed Tillodont by Marsh, armed with a pair of 
long incisors ; and the Deinocerata—an extraordinar y group possessing 
according to "Marsh the size of elephants, the habits of Fie 
but bearig a pair of long horn-like prominences on the snout, 
another pair on the forelead, and a single one on each cheek (Fig. 406). 
