9 
RHINOCEROS TICHORHINUS. 335 
Kirkdale, the remains of the large herbivorous quadru- 
peds were chiefly those of young animals, and such as 
would most easily fall a prey to the Hyzsnas, and be 
dragged by them into their den. 
Fig. 125 represents the 
Fig. 125. 
grinding surface of an upper 
molar tooth of the Rhinoceros 
tichorhinus, which was disco- 
vered in the Kirkdale ca- 
vern, and is now in the Bri- 
tish Museum. This tooth is 
the third of the series ; only 
the crown had been formed 
and had not made its ap- 
pearance above the gum. 
From its size, it was like- 
wise evidently the germ of 
: A Deciduous upper molar; nat. size ; Phi- 
a deciduous or milk tooth. noceros tichorhinus. Kirkdale cavern. 
The comparison of figure 
124, with figure 112, of a similar germ of an upper 
molar tooth of the Paleotherium medium, will illustrate 
the similarity of plan, and generic modification, of the 
structure of the teeth of the Rhinoceros, as compared 
with those of the more ancient Pachyderm. The outer 
wall of the crown is more even and less deeply indented ; 
the two valleys, a@ and 6, are wider in the Rhinoceros. 
Mastication first exposes the dentine at the summits of 
the ridges, and produces the two peninsular folds of enamel 
shewn in fig. 122. The continued wear of the tooth next 
insulates the posterior division of the transverse peninsula 
and simplifies it, as at 6 in the molar tooth from the cave 
of Kent’s Hole (fig. 126). As the shorter valley (a) is 
deepest at its extremity, further attrition exposes the 
