CHAPTER XX 
THE HOOK-LIPPED OR BLACK RHINOCEROS 
Rhinoceroses 
Family Rhinocerotidcd 
All of the living rhinoceroses are ponderous, thick- 
skinned mammals armed on the snout by one or two dermal 
horns. The structure of the horns is peculiar among mam¬ 
mals and quite unlike either the bony horns of the deer 
or the hollow, chitinous horns of antelopes and their kindred. 
The horn of the rhinoceros is made up of a compact, hard 
mass of agglutinated, hair-like fibres which are an outgrowth 
from the skin. The horns receive no bony support from the 
skull but rest on the nasal bones, where they are firmly held 
in place by their continuity with the thick skin of the 
snout. A slight concession, however, is made toward their 
support by the part of the nasal bones upon which they 
rest, this portion being set with numerous small, bony 
tubercles. So constant are these bony tubercles that pale¬ 
ontologists are enabled by such evidence to determine the 
presence and position of horns of extinct species. The 
horns are not strictly a family character, although so prom¬ 
inent a feature of the later forms, for some of the oldest 
genera were quite hornless. Rhinoceroses are evenly three¬ 
toed, and are members of the odd-toed or perissodactyl 
division of the hoofed mammals. In the structure of their 
feet they are fairly closely allied to the tapirs and distantly 
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