108—10 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
In this table, taking first the third true molar (the length of this tooth in the 
last column being calculated from the length of the preceding tooth), we find such 
a gradual variation in the size of this tooth that it appears to me that, unless we 
make six species of the six specimens, which would of course be out of the question, 
we cannot specifically separate any of these teeth on the ground of size alone. It 
may be noticed that in five out of the six fossil specimens, the last true molar is 
smaller than the corresponding tooth of the specimen of the skull of the living 
giraffe in the Indian Museum 1 : it is, however, quite probable that a considerable 
amount of variation in the size of the molars of the living species might be noticed 
if we had a sufficiency of specimens for comparison. It may further be noticed 
that in the fossil forms the last premolar is proportionately more elongated than in the 
recent species, a character by which it approaches the corresponding tooth in the 
sivathere and its congeners. 
Having now noticed the variations in the size of the lower molars of the 
Siwalik giraffe, we may proceed to consider their variations in form. 
In the specimen represented in figure 5 of plate XVI of this memoir, there 
are shown three perfect teeth, viz., the last premolar (p.m. 4), the first true molar 
(m. 1), and the last true molar (m. 3) ; the bases of the penultimate premolar 
(p.m. 3) and of the second true molar (m. 2) also remain. In the last true molar 
the accessory 4 column * is of very large size, and shows a distinct division into an 
inner (‘lobe’) and outer moiety ( 4 crescent’), with a cavity separating the two. In 
this tooth, as also in the specimen represented in figure 6 of. the same plate, the 
accessory 4 lobe ’ seems to be more completely developed than in the living species ; 
and a similarly large development is shown in all the other specimens of this tooth 
in the Indian Museum. In the specimen figured by Messrs. Ealconer and Cautley 
the accessory 4 column ’ is less complex, showing no distinct median pit. It is only 
in Megaceros, the giraffes' and the sivatheres, according to Professor Owen 2 , that 
this pit is developed in the accessory 4 column ’ of the last lower molar, which is much 
less complex in all other ruminants. The development of this column in the last molar 
of the ruminants is evidently a survival from the highly complex form this tooth 
presents in many of the older pig-like bunodont animals, and it is thus interesting 
to trace its greater relative development in the living giraffe, and this becoming still 
greater in its fossil representative, and in the closely allied sivathere and its 
congeners. 
The last true molar of the specimen represented in figure 5 of the same plate 
presents a minute tubercle in the 4 median valley, ’ entirely lacking in all the other 
specimens of that tooth : the first true molar in the same specimen exhibits a large 
tubercle in the same position. The large tubercle in this tooth seems to be very 
generally constant in both the recent and fossil species ; in the first lower true molar 
of the skull of a giraffe recently living in the Calcutta Zoological Gardens and now 
1 Another shull of an adolescent animal, formerly living in the Calcutta Zoological Gardens, has teeth slightly 
smaller than those of the specimen measured here. 
2 “ Odontography,” p. 535. 
