RHINOCEROS LEPTORHINUS. Sia 
(fig. 122), which has been worn down to about the same 
degree, it will be seen that, in fig. 141, the valley, 4, 
is wider at its commencement, and that the termination, 
where the letter is placed, is smaller and of a triangular 
Fig. 141. 
5th upper molar, fh. leptorhinus. Nat. size. Clacton. 
form: in the tichorhine molar it is much more expanded 
and bilobed by its extension towards the middle of the 
outer surface of the crown. The valley between these 
two terminal divisions, in the tichorhine molar, is so 
shallow, that the outer lobe is soon separated as an island 
of enamel, according to the pattern shown in fig. 126, 
and the valley then preserves an almost uniform width 
to the termination marked by the letter 6. In the upper 
molar of the leptorhine Rhinoceros, the valley is either 
divided by the wearing away of the shallow fold of ena- 
mel between the end of the narrow process entering the 
valley and the opposite bank, ¢e, whereby the end of 
the valley, 4, is wholly insulated, which change is shown 
in the molar of the Rhinoceros leptorhinus, from Crozes, 
