564 RHINOCEROS. 
penultimate grinder is in place, the sockets of the ante- 
penultimate molar, and of the three adjoining premolars, 
vacant ; that of the first premolar is obliterated: the whole 
of the socket of the second, and part of that of the third 
premolar are in advance of the back part of the symphysis. 
Besides this well-marked distinctive character, the present 
fossil displays the more convex curvature of the lower 
border of the jaw, its greater thickness in proportion to its 
depth below the premolar series. These differences are 
well brought out im contrast with the portion of jaw from 
the fresh-water beds of the Cromer Cliff, which belonged to 
a younger individual, and of which comparative admeasure- 
ments are subjoined :— 
Rh. leptorhinus. Eh, tichorhinus. 
In. Lin. In. Lin. 
Depth of jaw below the middle of third premolar 2 0 Sy W) 
Greatest thickness of the same part of the jaw ees) Le 8 
Depth of the jaw below middle of the penultimate molar 3 0 3. OS 
Antero-posterior breadth of penultimate molar 2 70 I 
55 »  oOflast molar . 2 38 1 8 
The last two admeasurements show the characteristic 
superior size of the molar teeth in the Lh. leptorhinus. 
Dr. Kaup has described and figured a portion of a lower 
jaw of a Rhinoceros discovered in the Rhine formations 
(‘im Rheine gefunden”), the left ramus of which, according 
to the figure,* contains the fourth, fifth, and sixth molars, 
the roots of the third and second, and the anterior root 
of the seventh molar; the second molar being in advance 
of the posterior commencement of the symphysis, as in 
the lower jaw of the Rhinoceros leptorhinus of Italy, figured 
by Cuvier (loc. cit. Bh. pl. ix., fig. 9), and as in the 
specimen from Clacton, figs. 132 and 133. 
Dr. Kaup, believing that in his Rhenish specimen the 
* “Akten der Urwelt,’ tab. ii, fig. 1, p. 6. 
