204 NEW YORK + ZOOLOGICAL VSOCiEiINe 
lyrate, straight or curved, annulated or studded with bosses, but 
they can never be forked, and are never deciduous. 
Which of these types of horn structure is the most ancient, that 
of the prong-horn, of the bovines, of the deer, or of the giraffe, 
we do not know, but the present evidence from paleontology in- 
dicates that the lines of descent diverged before horns came into 
existence. 
The giraffe and the kindred okapi form another great group 
of horned animals, representing an entirely different scheme of 
structure, the horns being persistent and permanently covered 
with velvet. It has been suggested that this horn is a mere gen- 
eralized structure, from which were evolved the antlers of the deer. 
This theory does not seem well supported by the facts, especially 
since a new species of giraffe has been recently discovered in 
Africa with an additional pair of horns, making five in all, the 
two extra horns being, like the third horn of the common species, 
quite rudimentary. 
The okapi also has two rudimentary horn cores, indicated ex- 
ternally by mere tufts of hair. All these horns are rudimentary 
and cannot be correlated with the antlers of the deer. 
A number of giraffine forms have been found in the Pliocene 
of Greece and India, and the Giraftidae appear to represent a sep- 
arate line of descent from a hornless ancestor of African ante- 
cedents. 
Nature made similar experiments in North America with the 
colossal Titanotheres, giving them paired horns on the extreme 
front of the skull, and with the Uintatheres, which had three pairs 
of horns. These efforts appear to have resulted in failures, since 
the groups no sooner obtained their full development than they 
rapidly became extinct. 
On the other hand the rhinoceroses, with unpaired horns, set in 
the median line of the skull, have survived to the present day. 
The horns of the giraffe and the bovines are present in both 
sexes, and are primarily weapons of defense, although the horns 
of male bovines are larger and stronger than those of the females. 
The branched and deciduous antlers of the deer and the prong- 
horn, on the other hand, are confined to the males, practically 
without exception,* and being functional only during the mating 
half of the year, are consequently secondary sexual characters. 
* The female Caribou has small antlers. 
