THE EOCENE PERIOD. 303 



peculiarity that they are arranged in a continuous series, with- 

 out any gap or interval between the molars and the canines; and 



Fig. 231. Aiioplotheriiiin commune Eocene Tertiary, France. (After Cuvier.) 



the back teeth, like those of all the Ungulates, are adapted for 

 grinding vegetable food, their crowns resembling in form those 

 of the true Ruminants. The genera Dichobune and Xiphodon, 

 of the Middle and Upper Eocene, are closely related to 

 Anoplothtrium, but are more slender and deer-like in form. 

 No example of the great Ruminant group of the Ungulate 

 Quadrupeds has as yet been detected in deposits of Eocene 

 age. 



Whilst true Ruminants appear to be unknown, the Eocene 

 strata of North America have yielded to the researches of 

 Professor Marsh examples of an extraordinary group (Dino- 

 cerata), which may be considered as in some respects inter- 

 mediate between the Ungulates and the Proboscideans. In 

 Dinoceras itself (fig. 232) we have a large animal, equal in 

 dimensions to the living Elephants, which it further resembles 

 in the structure of the massive limbs, except that there are 

 only four toes to each foot. The upper jaw was devoid of 

 front teeth, but there were two very large canine teeth, in the 

 form of tusks directed perpendicularly downwards ; and there 

 was also a series of six small molars on each. Each upper 

 jaw-bone carried a bony projection, which was probably of the 

 nature of a " horn core," and was originally sheathed in horn. 

 Two similar, but smaller, horn-cores are carried on the nasal 

 bones; and two much larger projections, also probably of the 

 nature of horn-cores, were carried upon the forehead. We 

 may thus infer that Dinoceras possessed three pairs of horns, 

 all of which resembled the horns of the Sheep and Oxen in 

 consisting of a central bony "core," surrounded by a horny 



