ADDITIONAL SIWALIK PERISSODACTYLA AND PROBOSCIDIA. 19 
premolar ; and it is merely necessary to assume the addition of an extra pair of 
columns to each of the true molars of the hunodont Artiodactyla to produce a 
dentition analogous to that of the simple-toothed mastodons. What the primal 
ungulate may have been that gave origin to the Proboscidia is at present unknown ; 
that it was intimately related to some of the eocene ungulates of America is almost 
certain, from the reseml^lance of their foot-structure to that of the elephants : the 
dentition of the former indicates, however, that they are probably a branch which 
diverged at an early date from the proboscidian stock, and are more intimately 
connected in this respect with the modern Perissodactyla. 
The mastodons, and still more the true elephants, may be regarded as animals 
retaining a very primitive type of skeleton, but whose dentition has reached a very 
high degree of specialization, d'he want of specialization in the skeleton may not 
improbal 3 ly be due to the huge size of these animals, whereby they have obviated 
the necessity of modifications on the primitive type of skeleton, which are necessary 
to produce a limb capable of the rapid flight of animals like the horse and the 
antelope. Their dentition has been gradually increasing in specialization in order 
to make the utmost possible use of the diet on which these animals subsist. 
The survival of the elephant in India, after so many highly specialized 
ungulates {e.g.-, Sivatherium) have entirely disappeared, seems to indicate the inherent 
vitality of a primitive form when once it has attained an amount of specialization in 
any direction (in this case in dentition, and corporeal bulk) to enable it to hold its 
own among other animals. 
Species 1 : Mastodon (Trilophodon) angustidens, Cuv. 
Yar. PAL^iNDicus, nobis. 
First record of occurrence in India . — It has been stated in the first volume* that 
some of the first-found mastodon remains from the Siwaliks were originally referred 
to M. angustidens.^ but were subsequently separated under the name of M. sivalensis. 
The only other notice referring to the occurrence of M. angustidens in India is one 
published in 1888^ referring to some of the specimens forming the subject of the 
present description. All these specimens, with one exception, which will be noticed 
in the sequel, were obtained from Dera Biigti. 
Third loiver true molar. — In order to determine the serial position of the different 
teeth described in the sequel it has been found necessary to commence with the last 
teeth of the series ; of which a specimen from the right side of the lower jaw is 
represented in plate IV., fig. 3. This tooth, which is in an intermediate stage of 
wear, was associated with the second upper true molar represented in figure 2 of the 
same plate : it carries four transverse ridges and a talon ( to) ; from which circum- 
stance, together with the shape of the crown, and the concave form of the worn 
masticating surface, it is evidently the last lower molar of a trilophodont mastodon. 
1 Page 248. 
^ ‘ Records,’ vol. XVI., pp. 161-2. 
