231—50 
SIWALIK AND NAEBADA PEOEOSOIDIA. 
shallow I each ridge is slightly convex anteriorly, and there is also a slight ten- 
dency to a blocking of the transverse valleys by incipient accessory tubercles 
bulging out at the centres of the transverse ridges. This curvature of the trans- 
verse ridges and consequent partial obstruction of the valleys seems to be a charac- 
ter which distinguishes the lower from the upper molars of Mastodon latidens. This 
character is well exhibited in the specimen under consideration, in the succeeding 
lower milk-molar represented in fig. 1 of the same plate, in the lower true molar 
represented in fig. 8 of Plate XXXI of the “Pauna Antiqua Sivalensis,” and 
in all the lower molars of this species contained in the Indian Museum. The 
enamel is quite smooth. The length of the second lower milk-molar (allowing a 
quarter of an inch for the broken talon) is 2-3 inches ; and its greatest width 1*7 
inches. The tooth is, therefore, slightly larger than the second upper milk-molar : 
a slight increase of size in the lower over the ujiper molars seems to be of very 
general occurrence in the Mastodons. 
Thwd upper milk-molar . — Continuing our serial description of the molars, the 
next tooth we have to consider is the third or last upper milk-molar, of which a 
specimen is represented in fig. 8 of Plate XXXVII. This tooth is the specimen 
referred to on page 72 of the eleventh volume of the “Eecords of the Geological 
Survey of India,” in connection with the presence of premolars in this species. 
The tooth was obtained by Mr. Theobald in the North-Western Punjab, and is im- 
planted in a fragment of the left maxilla ; above this tooth there was found in the 
l^one the germ of a smaller premolar tooth (represented in fig. 6 of the same 
plate), which would subsequently have displaced the larger tooth vertically, had 
the animal lived long enough. The presence of this premolar above the larger and 
more complex tooth proves that the latter belongs to the milk-molar series, and 
the presence of four ridges on that tooth shows that it must be the last of that 
series, or the first of the “ intermediate” molars of Dr. Palconer’s arrangement. 
The tooth has an oblong crown, slightly narrower in front than behind : the three 
first ridges are well worn, and their dentine disks have become partly united : the 
last ridge is somewhat worn on the inner side, and very slightly on the outer, 
while the posterior talon is almost intact. In profile the crown is strongly convex. 
The anterior talon, judging from the width of the first dentine surface, must have 
been small, while the posterior talon is of relatively large size and is double. The 
transverse ridges are very low and blunt, and extend almost straight across the 
tooth ; the valleys are open and entirely unobstructed by accessory tubercles. As 
is seen in the slightly worn last ridge, there is a longitudinal cleft, placed slightly 
on the outer side of the median line of the tooth, and dividing each ridge into an 
inner and an outer column, of which the inner is considerably the larger. In respect 
of this longitudinal cleft, and indeed in all characters (except of course size and the 
number of ridges), the tooth agrees precisely with the smaller second upper milk- 
molar represented in fig. 4 of the same plate. The enamel is corrugated. The 
length of the last milk-molar is 3*7 inches, and its greatest width 2’2 inches. 
