418 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Apr. 13, 
& 2,1) is defined by a cleft on the outer side of the tooth, but not on 
the inner side, fig. 3; here the abraded surfaces of ridges 1 and 2 are 
blended by wear into a common hollow field of smooth dentine (fig.1,a). 
There is a slight constriction near the part where the worn surface 
of the first ridge blends with that of the second; and this constric- 
tion, which may be detected in the succeeding ridges, I take to be a 
trace of that stronger one which more completely divides the trans- 
verse coronal ridge in the molars of better Mastodons into an inner 
and an outer part. A well marked tubercle (figs. 1 and 2, f) projects 
at the outer side of the base of the first ridge, 1, near the interspace 
between that and the second ridge. The second field of abrasion 
(ab. 1b. 2) although it broadens inwards to the common hollow, shows, 
before losing its individuality, a similar indication of constriction, or 
reciprocal inbending of the enamel boundary. The same indication, 
though feeble, 1s obvious in the succeeding ridges (3, 4, 5, a), which, 
by the unequal working of the lower grinder, show a broader field of 
dentine as they pass inward. The third and fourth ridges, which 
are entire, show their slightly undulated course from the outer to 
the inner side, which is lower and more worn. ‘The ridge at first 
inclines a little backward, then, at the indication of constriction, 
bends forward, and finally resumes the transverse course to the 
inner, lower and more worn side of the tooth. 
Now this character is not shown in the Mastodon elephantovdes, 
Clift, of which the antepenultimate upper molar (m 1) is figured, of 
the natural size, in plate 39. fig. 6, loc. cit..—nor in the homologous 
tooth of the same species, also from Ava, figured (one-third natural 
size) as of Elephas Cliftii, in the ‘ Fauna Antiqua Sivalensis’ of 
Falconer and Cautley, pl. 30. fig. 2. 
From the general conformity of character of the transverse ridges 
in the last three molars (m1, m 2, m 3) of this species, it is unlikely 
that so marked a difference of course and configuration of the ridges 
should exist in the second grinder, answering to d 3, of the same 
species. 
Nevertheless in the number of ridges in a given tract of the 
grinding-surface, in their height and breadth of base, and in the 
absence of intervening cement, the conformity of the Chinese molar 
with the grinders of the Mastodon elephantordes is close. The enamel 
also shows the same vertical linear impressions and ridges, by which 
we may reckon that the summit (say, of the fourth ridge in the tooth 
here described), if it were unworn, might be cleft into from thirteen 
to fifteen small mamille. 
This structure is well shown in the full-sized figure of the upper 
molar (m1) of Mastodon elephantoides, Clift (in plate 39. fig. 6, 
Trans. Geol. Soc. vol. ii. second series). 
In a tooth of an allied species from the Siwalik tertiaries, homo- 
logous with the specimen under description, figured in the ‘ Fauna 
Antiqua Sivalensis,’ pl. 29. figs. 3, 3.a, as of Elephas bombifrons, but 
subsequently referred by Falconer to his Hlephas (Stegodon) msignis*, 
* Palxontological Memoirs, vol. i. p. 459, in description of plate 29. 
