ANCESTRY OF RODENTIA 
ments, the outer pair of incisors had been greatly reduced, and the second 
pair been much enlarged. Moreover, while those of the earliest tillodonts 
do not seem to have grown from persistent pulps, the incisors of the later 
genera (as Tillotherium) did do so. Similar features tending toward the 
modern rodents are seen elsewhere in the structure. Nevertheless, the 
tillodonts seem not to have been in the direct line of ancestry, and 
came to an end with the close of the Miocene period. The largest 
of them was the most recent form, Tillotherium, which was as big 
as a small bear. 
We may now take up the Rodentia in order, beginning with 
the Duplicidentata, because they are of a more primitive type, 
as shown by the dental 
resemblance to the tillo- 
donts, in having two pairs 
of incisor teeth in the 
upper jaw, although the 
inner pair is small and 
hidden behind the big 
outer pair; and sometimes 
there appear in earliest 
infancy traces of a third 
pair. 
The hares and rabbits 
form a compact family 
(Leporide) of some sixty +. Ae 
species, scattered in all EUROPEAN HARE. 
divisions of the globe ex- 
cept Australasia and Madagascar; but only one species occurs 
in South America, and the family is most numerous in north- 
erly regions, where these animals form an important food 
resource for man and beast. All are much alike in the long, 
high-haunched hind legs, which give great leaping and dodg- 
ing power; tall, erectile ears; divided upper lip; short scut; 
and grizzled gray brown coat, with various specific markings 
of white and black. The only exceptional one is the “hispid” 
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