374 RHINOCEROS. 
Department du Gard, figured, but not recognized as such, 
in the ‘Ossemens Fossiles,’ tom. ii., pt. 1, Rhinoceros, pl. 
xiil., fig. 4; or the whole valley is gradually diminished 
in depth, without the separation of an enamel-island, but 
continuing to manifest its characteristic wide beginning, 
as is shown in the upper molar from the same locality 
in France, figured by Cuvier, tom. cit. pl. xiii, fig. 5. 
These varieties depend on the varying depth of the narrow 
part of the valley at the end of the small intruding pro- 
montory, and they are exemplified in two of the molars 
from Clacton: but neither of the patterns of the grinding 
surface of the upper molars of the &h. leptorhinus, pro- 
duced by the effects of mastication upon the valley, 0, 
are presented by the molars of any of the recent Rhino- 
ceroses, except the two-horned species of Sumatra. In 
this the valley, 4, very closely resembles in its form and 
intruding promontory that in the upper molars of the 
leptorhine Rhinoceros; but the ridge on the outer side 
of the tooth, corresponding to that marked d’ in fig. 141, 
is much more produced, and the adjoining convexity at 
the middle of the outer surface is flatter. 
But to proceed with the comparison between the upper 
molars of the extinct tichorhine and leptorhine Rhimoce- 
roses; the lateral valley, a, is wider and deeper at its 
commencement, and shallower at its termination in fig. 
141 than in figs. 122 and 126; it is not so soon, 
therefore, worn down into a second island of enamel, 
like that shown in the molars of the tichorhine Rhino- 
ceros figured by Cuvier, loc. cit., pl. xii., figs. 1 and 6: 
the inner termination of the lobe, c, is broader and more 
bulging in the leptorhine Rhinoceros, the outer longi- 
tudinal ridge, d’, is more produced, and the anterior basal 
ridge, 7, is longer and better developed. The small 
