INTRODUCTORY OBSERVATIONS. xvii. 
[%. 8].), and in plate XLII, of the first volume of the present work.^ In the 
unworn m.2 (woodcut fig. 8j accessory tubercles («) are present on the outer side of 
a a a 
Fig. 8. Ifastodon perimensis. The second left upper true molar, in an unworn condition ; from the Siwaliks 
of Perim Island. §. Indian Bluseum (No A. 355}. a. external accessory tubercles. The lower border of 
the figure is the inner border of the specimen. 
the median longitudinal cleft, which are attached to the hinder side of each ridge, 
and gradually diminish in size from the first to the fourth ridge : these tubercles are 
also observable in m- (supra vol. I. pi. XLIL), but are absent in M. latidens and M. 
cauileyi. Tlie inner column of each ridge has no distinct accessory tubercle on its 
posterior aspect in the specimen figured in woodcut fig. 8, but a large one is present 
to each ridge in the one figured in the “ F.A.S.” pi. XXXI. figs. 9, 9a. In all the 
above-mentioned teeth the ridges are still higher, and more nearly vertical than in 
M. cautleyi, while the posterior surface of the outer column* of the first ridge is less 
hollowed, and the summit of the unworn inner column of the same frequently does 
not form a complete V (woodcut fig. 8) : the hind talon of the ‘intermediate’ molars 
is relatively larger (compare woodcut fig. 8 and Falconer’s “ Palaeontological 
Memoirs,” vol. I. pi. IX. fig. 6 with woodcut fig. 5 and vol. I. pi. XL. of the present 
work) ; the main columns of the ridges have a more decided tendency to an alternate 
arrangement, and the valleys are generally blocked to a greater extent by accessory 
tubercles ; cement is, moreover, present in much greater quantity.^ The third true 
molar figured in vol. I. pi. XLII. is long, narrow, and tapering posteriorly, and 
carries five ridges and a complex hind talon, but a specimen in the British Museum 
(M. 256) is wider posteriorly. All the teeth agree with those of M. cautleyi in pre- 
senting trefoils on their earlier inner columns, but their crowns are relatively narrower. 
Having now pointed out the characters in which the present form differs from 
M. latidens and M. perimensis, it remains to indicate how close is the resemblance 
between the molars of certain examples of the three forms. In some molars of M. 
1 The specimen figured in vol. I. pi. XLI. fig. 4 of the present work as of M. perinwisis has been shown in vol. 
III. p. 151 to belong to M. sivalensis. 
In some specimens (e. tj. the one represented in woodcut fig. 8) the cement has fallen out. 
