1 8 The Mammals of Colorado 
five years. The fully matured horn has a strongly recurved 
and somewhat incurved tip and bears a well-developed prong 
in front. . . . The mechanical factor in the dropping off 
of the horns appears to be the rapid development of a new 
horn on top of the horn-core and beneath the old horn which 
is about to be shed. This newly growing horn pushes the old 
one upward, loosening it from the horn-core to which it has 
been attached by the continuity of its substance with that of 
the horny layer of the skin covering the core. ... In the 
autumn of the year the horns of the Antelope are always 
loosely attached to the bony core, and can be pulled off with 
but little effort." The horns are shed in autumn or early 
winter, and old bucks drop their horns earlier than younger 
animals do. 
Family CERVID^E 
Frontal appendages, when present, in the form of antlers; 
these are outgrowths of true bone, and are covered during 
growth with a vascular sensitive skin, the velvet, which peels 
off when growth is completed; antlers shed annually, or at 
any rate periodically, and in most cases branched; dentition: 
i. f ; c. ; pm. |; m. f ; anterior molar of both jaws brachy- 
odont (i. e., short crowned); upper canines usually present 
in both sexes; the lateral digits of both fore and hind limbs 
almost always present; gall bladder absent. 
Key of the Genera 
A. Size larger, total length loo or more; antlers with brow and 
bez tines, Cervus, p. 24 
B. Size smaller, total length 72 or less; no brow or bez tines on 
antlers, Odocoileus, p. 18 
Genus ODOCOILEUS (Gr. odous, tooth + koilos, hollow) 
Odocoileus Rafinesque, Atlantic Jour., i., p. 109 (1832). Type, 
O. americanus . 
This genus contains a group of the Deer family charac- 
