PART 1.] 
Lydehl'er : Nvtkes of Siwalik Mammals. 
09 
The next question, therefore, is to find some character which distinguishes the 
molars of the three last-named genera. Now, if we turn to page 442 of Owen’s 
“ Odontography,” we shall find that in ti’cating of the molars of the mandrils, the 
author observes that the true molars “ progressively increase in size from the first 
to the third;” and on the next page, that “the smaller Baboons, of the genus 
Maeacus, repeat on a smaller scale the dental characters of the mandrils.” Now, 
with all due deference to the author of the valuable work under notice, it does not 
appear to me that the characters given above are always characteristic of the genus 
Macaeus, because if we refer to the table of measurements given above (and 
several specimens have been compared), we shall find that in M. rhesus the first 
molar is smaller than the second, which agrees with Professor Owen’s state¬ 
ment, but that the third is smaller than the second, which does not. 
In treating of Semnopithecus, Professor Owen remarks on page 443 that 
“ the first molar is equal to the second.” Now, in the. table given above, it will be 
seen that in S. eutellm the first molar is smaller than the second; and in the 
figm-ed specimen of the dentition of this genus given in figure 5, plate 116, of the 
“ Odontography, ” the first molar is also somewhat smaller than the second. 
These characters do not, therefore, seem to be of any great value as afEording 
means of distinguishing between the genera in question. 
It does, however, appear that in Semnopithecus there is a tendency for the 
molars to be of more equal size than in Macacm, in which the first is always 
small and the second large; thus in S. phayrei and S. siamensis the first and 
second molars are of equal length; while in 8 . entellus and 8 . cephalopterus the 
second and third are of equal length, and the first slightly smaller. I have seen 
no instance in the genus Semnopithecus in which in the same jaw the first molar 
is smaller than the second, and the second larger than the third. 
In the genus Gercopithecus there appeal’s to be gi-eat equality in the size of the 
upper molars; thus in C. sabceiis the three are of equal length; in G. pluto the 
two first are equal, and the third slightly smaller; and indeed in all the specimens 
that I have seen the two first are of equal length. 
It is therefore apparent that the fossil specimens cannot belong to Gercopithe- 
cus; and it is also apparent that in the relative length of the molars they 
do not agree with any species of Semnopithecus, but that they do agree with 
Macacus rhesus; the evidence then so far is, that the fossils belong to the latter 
genus. 
Now, with regard to the form of the teeth : in Semnopithecus and Macacus, 
the two first upper molars appear to me to be absolutely indistinguishable in the 
two genera: the last molar of Macacus, however, has the posterior talon-ridge 
forming a complete semicircle, which connects the two posterior cones of this 
tooth; in the corresponding tooth of Semnopithecus, on the other hand, this talon- 
ridge starts from the postero-internal cone, and curves upwards and outward,s, to 
the base of the outer side of the crown, its curve forming only a quarter in place 
of half a circle, and not being connected with the outer cone at all. The 
last molars of the fossil specimens agree with the last molar of Macacus in this 
respect, and there seems, therefore, to be no doubt from this and the previou.s evi¬ 
dence that the specimens reallj’ belong to that genus. 
