203—22 
SIWALIK AND NAEBADA PEOBOSOIDIA. 
in front than behind ; tlie triturating surface carries two main transverse ridges 
separated on the outer side (top of figure) by a wide and open valley, but on the 
inner side in contact. Each of tliese transverse ridges is mesially divided by 
an antero-posterior cleft into a distinct inner and outer column, of which the latter 
is the higher. In both columns of the anterior ridge the enamel has been per- 
forated by trituration; the inner column of the second ridge also exhibits a 
considerable islet of dentine, while tlie outer column of the same ridge has 
merely its summit obliquely abraded, but the enamel not perforated : the den- 
tine islets are in the form of irregular disks. In advance of the first transverse 
ridge there is a small and narrow talon, somewhat broken in the specimen, and 
on which the dentine is exposed by wear; behind the second transverse ridge 
tliere is also another talon, of unusually large size, and carrying a distinct tubercle 
at its inner extremity. There is a small tubercle at the outer extremity of the 
main transverse valley. The length of this tooth is 1“8 inches and its greatest 
width 1'6 inches. 
Third upper milk-molar. — The larger tooth (fig. 3) immediately succeeded the 
lu’eceding specimen in the young cranium, and is consequently the third, or last, 
upper milk-molar of the left side. This tooth is implanted in the maxilla by four 
distinct fangs ; the crown is oblong in shape and carries three transverse ridges and 
fore-and-aft talons. The presence of these three transverse ridges on this tooth, 
which is the first of the ‘‘ intermediate ” molars, proves that the cranium in question 
belonged to a trilophodont Mastodon ; the corresponding and two succeeding teeth 
of a Tetralophodon would of course carry four ridges each. Each ridge, as in the 
preceding tooth, is mesially divided by an antero-posterior cleft into an inner and 
an outer column, and each ridge carries five cusps or denticles. The inner portion 
of both the second and third ridges is placed somewhat obliquely to the long axis 
of the tooth ; the postero-internal angle of the last ridge joins the hind talon ; there 
is a small but distinct tubercle on the hinder side of both the first and the second 
ridges ; these tubercles at their junction vdth the centre of the next ridge very 
slightly block the bases of the transverse valleys ; the latter are, however, mainly 
characterized by being fairly free and open. The anterior talon is small, and its 
cusps indistinct ; the posterior talon is larger, and its cusps, especially the three on 
the inner side, are of large size and well defined. There is a faint trace of 
abrasion on the anterior ridge of this tooth, otherwise it is untouched by Avear. 
The length of the specimen is 3’04i inches and its width 2 inches. 
Young cranium. — The imperfect cranium of a young individual of Mastodon 
falconeri, to which the two last described milk-molars belong, is in much too 
damaged a condition to afford a figure, or indeed any idea of the form of the perfect 
cranium. Behind the tooth, which lias been described above, there occurs in that 
cranium the germ of a third tooth which, like its predecessor, carries three transverse 
ridges, and which from its position must be the first true molar. This tooth agrees 
in general characters exactly with the last milk-molar described above ; as it cannot 
