30 lieconh of ihe Geological Survey of India. [vol. xir. 
Table sliotcing relative lengths of first tq)per true molar and last preinolar in the higher 
1‘rimaies. 
i 
1 
Length of 1 st : 
molar. 
Length of last 
premolar. 
! 
! i 
Difference between 
I these lengths. 
Pioportionate ' 
length of P. M., i 
4 on scale of 
Siwalik jaw. 
Excess of real 
over proportion¬ 
ate length. 
Siwiilik jaw 
... 
0-45 
0-30 
0-15 
0-30 
0-00 
Human S 
... 
... 
0-36 
0-25 
0-11 
0-24 
0-01 
Troglodytes niger S 
... 
0'45 
0-32 
0-13 
0-30 
002 
Simla satyrus $ ... 
... 
0-50 
0-39 
013 
0-33 
O-OG 
Ditto $ ... 
0-43 
0-35 
0-07 
0 23 
0-07 
Hylobates syndiictylus 
• •« 
... 
0-28 
0-25 
0-03 
0T8 
0-07 
Troglodytes gorilla 
... 
... 
0-55 
0-48 
0-07 
0-36 
012 
Tlie first of tliese two tables exhibits merely the absolute dimensions of the 
different teeth ; while the second is intended to show the relative lengths of the 
first molar and the last premolar in the same gi-onp. In the fourth column of 
that table is given what w'ould be the length of the last premolar, if that tooth 
bore the same relationship as regards length to the first true molar, which it does 
in the Siwalik jaw. From that table it will bo seen that the new jaw is distin. 
guished from the jaws of all other Primates by the relative smallness of the 
antero-posterior diameter of the last promolar; this shortness is in excess of what 
occurs in man, in which the same premolar is relatively shorter than in all the 
other higher Primates ; next to man in this respect comes the chimpanzee, then 
the orang, and last of all the gorilla; and it is worthy of notice that the two 
species which (excepting man) exhibit the greatest variety in this respect are 
placed in the same genus. Professor Owen, at page 446 of his “ Odontography,” 
notices the small antero-posterior diameter of the premolars in the chimpanzee, 
as distinguishing it from the orang, and approximating it to man. The new 
Siwnlik jaw, as we have seen, stands on the opposite side of man to the chimpanzee 
in this respect, and therefore should be still more removed from the orang. The 
new jaw agrees wdth that of the orang, gorilla, and chimpanzee, in having the 
molar series approximately straight, and with no indications of the horse-shoe 
form which occurs in the human subject; it therefore belongs to a true ape. 
Turning our attention once again to the first of the two tables of measure¬ 
ments, we may note in what other respects the fossil jaw resembles or differs 
from the jatvs of the orang, the chimpanzee, the gorilla, and man. In regard to 
