RHAHINOCEROTIDE #68 
aborted, so that the contour of the crown is triangular. Head 
large, skull elongated, elevated posteriorly into a transverse occi- 
pital crest. No postorbital processes. Nasal bones large and stout, 
co-ossified, and standing out freely above the premaxille, from which 
they are separated by a deep and wide fissure; the latter small, 
generally not meeting in the middle line in front, often quite rudi- 
mentary. Tympanics small, not forming a bulla. Brain cavity very 
small for the size of the skull. Vertebre: C 7, D 19-20, L 3, 
S 4, C about 22. Limbs stout, and of moderate length. Three 
completely developed toes, with distinct broad rounded hoofs on each 
foot (Fig. 151, p. 36S), some fossil forms having a fourth in the 
manus. Eyes small. Ears of moderate size, oval, erect, prominent, 
placed near the occiput. Skin very thick, in many species thrown 
into massive folds) Hairy covering scanty. When one horn is 
present it is situated over the conjoined nasal bones ; when two, the 
hinder one is over the frontals. These horns, which are of a more 
or less conical form and usually recurved, often grow to a great 
length (three or even four feet), and are composed of a solid mass 
of hardened epidermic cells growing from a cluster of long dermal 
papilla. The cells formed on each papilla constitute a distinct 
horny fibre, like a thick hair, and the whole are cemented together 
by an intermediate mass of cells which grow up from the interspaces 
between the papille. It results from this that the horn has the 
appearance of a mass of agglutinated hairs, which, in the newly 
srowing part at the base. readily fray out on destruction of the 
softer intermediate substance ; but the fibres differ from true hairs in 
growing from a free papilla of the derm, and not within a follicular 
involution of the same. mE 
The large lower cutting - 
teeth of the typical Rhino- 
ceroses have been very gener- 
ally regarded as incisors, but 
comparison with fossil allied 
types, in which three lower in- ¢ 
cisors and canines are present, 
leaves little doubt but that 
they are really canines. The 
upper molarteethpresent some 
amount of specific variation ; Lae nem ese Sere ied 
thus while one type (Fiz. pee = ecuigies anise tee eee 
168, .4) has only a’ simple crotener; 2, r 
* erotchet ” projecting from valley; |, anterior intermediate column. Ozher 
the posterior transverse ridge "=" FS He PS 
into the median valley, in others (Fig. 168, £) this crotehet joins a 
“erista,” or “combing-plate.” projecting from the outer wall to cut 
off a distinet fossette from the median valley. Occasionally, however 
