EIGHTH ANNUAL REPORT. 203 
The existence of Paleomeryx in America proves that as early 
as the Miocene, deer existed here, which could readily have given 
rise to Odocoileus. This, taken together with the fact that there 
is no known Old World line which suggests Odocoileus, would 
indicate an American origin for the latter animal. Nevertheless 
Odocoileus is not found fossil earlier than the Middle Pleisto- 
cene, when both O. virginianus and O. hemionus appear at the 
same time with Cervus. 
THE PRONG-HORN OR AMERICAN ANTELOPE. 
Of the prong-horn, Antilocapra americana, and its aberrant 
characters, much could be written. It is not an antelope, not even 
in the sense that the mountain goat is an antelope, but stands ab- 
solutely alone, and represents one of Nature’s efforts to evolve a 
horned animal. It certainly has developed all its peculiar charac- 
ters on this continent, but has not yet been found fossil earlier 
than the Lower Pleistocene. 
Although the family Antilocapridae has but one genus and a 
single species, with a northern and southern form, yet its charac- 
ters are so extraordinary that it is properly assigned to a rank of 
equal value with the Cervidae and the Bovidae. 
The horns of the prong-horn differ greatly from those of the 
other hollow-horned ruminants, but not so much as do the horns 
of the latter from the antlers of the deer, but all the structural 
characters of the prong-horn, other than its exceptional horns, 
indicate an affinity with the bovine antelopes rather than with 
the deer. 
First we have the peculiarity of the horns being placed directly 
over the eye, a character which the prong-horn seems to share 
with the American Miocene antlered antelopes or merycodonts. 
Next, the horn structure itself is unique. It is not a bony process 
of the skull, like the antlers of the deer, but grows over a persist- 
ent horn-core. It is pronged, and, above all, is annually shed not 
long after the rutting season. 
The horns of the Bovidae are a process of the skin, of the same 
material as hoofs, claws and nails. But the horns of the prong- 
buck are composed of agglutinated hair, paralleling in this respect 
the horn of the rhinoceros. However, hair is also an epidermal 
process, and the horns of the prong-buck are histologically closely 
related to those of the Bovidae. 
The horns of other hollow-horned ruminants may be spiral, 
