DESCRIPTION OF PLATES. 5 
worn out; they were four in number. Jastodon latidens is the form 
most nearly allied to HL. Cliftii, and, through that species, to the true 
Elephants.—B.M. 
Length of last tooth, 5°5 in. 
Fig. 9.—Mastodon Ohiotieus. Vertical, section of last upper molar. 
It consists of four principal ridges and a small talon lobe. The ridges 
are transverse, terminating in a trenchant edge; the ivory segments are 
in regular angular lobes; the layer of enamel is of uniform thickness, 
and the hollows between the ridges are very wide and open, being 
almost rounded at the bottom. There is only an exceedingly thin crust 
of cement, continued over the fangs in greater thickness. The common 
plane of the grinding ridges of the crown is nearly horizontal. M. 
Ohioticus constitutes the terminal link in the chain, and through 
Dinotherium establishes a passage into the ordinary Pachydermata. 
B.M. 
Fig. 10 a.—Mastodon Sivalensis, from the Sewalik hills. Vertical 
section of last upper molar. The ridges are more complex in their 
composition than in M. latidens. The crown is bisected by a longitudinal 
furrow, each division of the ridge being composed of a pair of contiguous 
conical mammille placed more or less alternately. The hollows are in 
consequence interrupted. There are five principal ridges, with a subor- 
dinate ridge in front, and a talon ridge behind. Hight divisions of the 
ivory may be counted in the figure, the smaller segments arising from 
the direction in which the section has been made through the alternate 
mammille. The ridges are approximated, and the enamel bears a 
large proportion to the conical lobe of ivory which it invests. The 
cement is entirely wanting, except in the bottom of the clefts—B.M. 
Length of tooth, 7 in. 
Fig. 10 6.—Mastodon Sivalensis. Vertical section of greater part 
of last lower molar. The tooth differs from the corresponding upper 
molar only in being complicated with an additional ridge-—B.M. 
Fig. 11.—Dinotherium Indicum (Fale.), from Perim Island. Ver- 
tical section of posterior ridge and talon of the penultimate lower 
molar, left side. The internal structure exhibits the same agreement 
with that of the European Dinotherium, as is indicated by the external 
form. The only perceptible difference is, that the angle formed by the 
ridge of the ivory is more acute, and the enamel thicker in the Indian 
species. The centre is occupied by a rhomboidal core of arenaceous 
matrix marking the form of the unossified pulp nucleus. This tooth 
is described and figured in Dr. Falconer’s Memoir on Perim Island 
Fossils. 
Fig. 12.—Dinotherium giganteum (Kaup), from Eppelsheim. Ver- 
tical section of entire penultimate lower molar, consisting of two 
transverse crenulated ridges, and a talon ridge, while in the equi- 
valent molar of Mastodon Ohioticus there are three principal ridges. 
Corresponding to the smaller number of divisions the ridges are more 
widely separated, less elevated, and broader at their base, while the 
interspaces are also wider and more open than in the North American 
Mastodon. The layer of enamel is of similar thickness, and there is 
no appreciable crust of cement. The correspondence is followed out 
in the form of the subordinate heel ridge. D. Jndicum, however, is 
the species most nearly allied to W. Ohioticus.—B.M. 
