308 PROFESSOR OWEN ON SOME SPECIES OF THE EXTINCT GENUS NESODON. 
thicker enamel. The outer surface of the anterior lobe of p 2, and of both lobes of 
p 3, is less convex in Nesodon Sulivani than in Nesodon imhricatus. 
Upper Molar Tooth ^Nesodon magxus. 
The superiority of size, indicated by the portion of tooth in Plate XML figs. 21, 
22 and 23, of the animal to which it belonged, over the Nesodon Sulivani, is too 
considerable to be interpreted as a mere variety in a wild animal. That the dental 
fragment in question belongs to a species of the present genus, is to be inferred by 
the close resemblance of the enamelled exterior surface of the tooth to the same 
part in the upper molars of the known species of Nesodon. 
This remarkable fragment, which might pardonably have been mistaken for part 
of the tooth of a Rhinoceros, is the outer side of the crown of an upper molar, worn 
low down, showing the natural termination of the enamel upon the base of the fangs* 
which, with the inner part of the crown itself, have been broken away. 
The remaining part of the crown presents its grinding surface worn obliquely to 
the enamel, which forms almost a trenchant edge; the produced and ridge-like 
anterior angle (fig. 23, «)is preserved; the longitudinal obtuse ridge of enamel (fig. 21,^) 
on the outside of the crown, near that border, and the gently convex surface of the 
broad part of the crown behind the ridge, equally repeat the characters of the oumr 
surface of the upper grinders of Nesodon, as exemplified in the smaller species 
(fig. 5, di). A narrow and low ridge of enamel is continued from the base of the 
longitudinal rising, h, along that of the rest of the crown, 3 or 4 lines from the 
radical border of enamel, and then curves upwards along the hinder border of the 
crown to the posterior angle of the outer part of the grinding surface, c. 
The crowns of the upper molars of the Nesodon oviniis do not show this marginal 
ridge. 
The breadth of the remains of the crown of the upper molar of the Nesodon 
magnus at the grinding surface is 2 inches 8 lines ; the length of the enamelled part 
is 2 inches 4 lines. The resemblance of the fragment in its shape, and in the disposi- 
tion of the outer plate of enamel, to the similarly sized upper molar of the Rhinoceros 
is very close ; but the characteristic thinness of the crown, as shown by the bend of 
the enamel at the fore-part of the fragment, fig. 23, the thinness of the enamel, and 
the uniform oblique abrasion of the outer part of the grinding surface, are all maiks 
of closer resemblance to the upper molars of the genus Nesodon. 
The surface of the enamel in the present tooth of Nesodon mag 7 ius is polished, but 
is minutely wrinkled, especially towards its basal termination ; it show's no strice of 
growth. 
The remarkable portion of molar tooth here described and figured indicates a 
species of Nesodon of a size equal to that of the largest extinct species of Rhinoceros, 
which genus we may suppose the Nesodon to have represented in the American 
Continent during the pliocene and perhaps miocene periods. 
