RHINO CER OSES. 
463 
Succession of 
Teeth. 
It is further reported that the tapir is not unfrequently successful; and, in 
any case, many of these animals are killed with the marks of jaguar’s claws 
on their backs. 
Before leaving these animals, it may be mentioned that the 
whole of the four premolar teeth on each side of the upper jaw are 
preceded by milk-teeth, whereas in the pig and other Even-toed Ungulates the first 
of these teeth never has a deciduous predecessor, as, indeed, is the case with other 
groups of Mammals. Some rhinoceroses, however, resemble the tapirs in having 
the first premolar preceded by a milk-tooth, although this seems to be merely 
an individual, and not a specific peculiarity. 
The Rhinoceroses. 
Family RlIINOCEROTIDH. 
Although inferior in length of body, and probably also in weight, to the 
hippopotamus, the larger species of rhinoceros exceed it in height, and, there¬ 
fore, vie with it in claiming the position of being the Mammals next in point 
of size to the elephants. Unlike the tapirs, the various species of rhinoceros, all 
of which are now confined to the Old World, differ very markedly from one 
another in structure—so much so, indeed, that by many writers they are divided 
into several genera; and there is also considerable disparity in point of size. In 
spite, however, of these minor differences, all these animals are so much alike in 
general appearance, that it seems preferable to include the whole of them in the 
single genus Rhinoceros. All the existing rhinoceroses differ from tapirs in having 
but three toes on both fore and hind-feet, but since there are some extinct species 
with four toes to the front limbs, this point of distinction cannot be regarded as a 
very important one. The presence of one or two horns in the middle line of the 
front of the head might at first sight be regarded as a more valuable diagnostic 
character, but since these appendages are always or frequently absent in the 
female of one of the living Indian rhinoceroses, and are invariably wanting in 
certain extinct kinds, it will be obvious that other features must be sought that 
will distinguish these animals from the tapirs. 
Such characteristics are to be found in the cheek-teeth, of which 
two from the upper jaws of certain extinct species are represented 
in the figures on next page. In the molar teeth of the upper jaw the two outer 
columns have completely coalesced so as to form a continuous external wall to 
the crown; this wall being sinuous, and in some cases (as in the upper figure) 
forming a prominent buttress at the front outer angle of the crown. From this 
outer wall proceed two continuous oblique transverse ridges, separated from one 
another by a deep valley, interrupted by projecting processes from one or both 
ridges, and sometimes also from the outer wall. This middle valley is usually 
quite free from cement; and its form, as likewise the relative height of the whole 
crown, varies considerably in the different species. Instead of having the simple 
transverse ridges found in those of the tapirs, the lower cheek-teeth of the 
rhinoceroses have a pair of crescents, placed one in front of the other. On each 
Teeth. 
