243—62 
SIWALIK AND NADBADA PEOBOSCIDIA. 
two teeth are further distinguished hy their wear ; in the European tooth the dentine 
surfaces of the last ridge are much larger than in the Indian tooth, showing that 
the plane of wear is less oblique in the former than in the latter. Again, in the 
tooth of M. perimensis, the dentine surfaces of the two columns of each ridge 
seem to unite at an early period of wear, and form a straight hand across the tooth ; 
and there is consequently no distinct trefoil in the outer column of the second 
ridge, which is so conspicuous in the tooth of M. longirostris when well worn, as 
in Kaup’s specimen. 
Last upper molar. — No specimen of the last upper true molar of Mastodon 
perimensis is figured either in the “ Palseontological Memoirs” or in the “ Pauna 
Antiqua Sivalensis,” although the cranium represented in Plate XXXVIII of the 
latter work shows the base of the last true molar, the crown having been hammered 
off. The magnificent molar of a Mastodon represented in Plate XLII of this 
memoir was collected by Mr. Theobald in the Punjab, and is the last left upper 
true molar, as may be determined from its form, size, and number of transverse 
ridges. The tooth is long and narrow, which character alone is sufficient to dis- 
tinguish it from the corresponding tooth of M. latidens ; the anterior ridge is the 
widest, the transverse diameter of the crown gradually decreasing from this point 
to the posterior extremity, where the tooth is rounded regularly off. This tooth carries 
five transverse ridges, and a small posterior talon ; there is also a small step or 
ledge at the anterior extremity, which doubtless represents an anterior talon. The 
ridges are very tall, and are divided by the median cleft into conical inner and 
outer columns. The two first ridges have been partly worn, and exhibit well the 
uneven rate of wear of the two sides of the crown, which we have seen to be 
characteristic of the molars of this species. The general arrangement of the 
columns of this tooth is much the same as we have seen to prevail in the earlier 
teeth of the species ; the inner column of each ridge wearing into a trefoil, and 
the outer into an oblong. A few accessory tubercles are developed at the bases of 
the outer extremities of the transverse valleys, which are not found in the anterior 
teeth. The fifth ridge is narrower and lower than any of the preceding ridges, 
and the hind-talon consists of three small low tubercles, the largest of which is 
placed in front and on the inner side of the .others. The tooth shows the thick 
enamel, and the small amount of cement so characteristic of the species. In the 
following table the dimensions of this tooth are given, together with those of the 
corresponding tooth of the opposite side of M. longirostris represented in fig. 9 
of Plate XVIII of Kaup’s “ Ossements Eossiles du Museum de Darmstadt.” 
M. perimensu. M. longirostris. 
Length 9'6 8'9 
Greatest width . . . . . . . , . . . 3'7 3'9 
Height of third ridge 2'8 2’6 
Comparison with M. longirostris. — Prom these measurements it wiU be seen 
that the last upper true molar of M. longirostris is shorter and broader and has 
