Chap. Y. MONKEYS OF OLD AND NEW WORLD. 325 
be interesting, therefore, to see how differently the sub- 
sequent creations of species have proceeded in each of 
the separated areas. 
The American monkeys are distinguished, as a body, 
from all those found in the Old World. Upon this 
point, there is no difference of opinion amongst modern 
zoologists. It is not probable, therefore, that species 
of the one continent have passed over to the other, 
since these great tracts of land received their present 
inhabitants of this order. The American productions pre- 
sent a cluster of forms, namely, about eighty-six species, 
separated into thirteen genera, which although greatly 
diversified amongst themselves, in no case show signs 
of near relationship to any of the still more diversified 
forms of the same order belonging to the eastern hemi- 
sphere. One of the two American families (Cebidse) 
has thirty-six teeth, whilst the corresponding family 
(Pithecidse) of Old World apes has, like man, only thirty- 
two teeth ; the difference arising from the Cebidse 
having an additional false molar tooth^ to each side 
of both jaws. This important character is constant 
throughout all the varied forms of which the Cebidge 
family is composed ; being equally present in the pre- 
hensile-tailed group, with its four genera containing 
twenty-seven species, differing in form and clothing, 
shape of claws, mental characteristics, and condition of 
thumb of the anterior hands ; and in the true Cebi and 
the group of Sagouins, with six genera and twenty-four 
species, including day apes and night apes, short 
* False molars, or premolars, differ from true molars, through being 
preceded in growth by milk teeth. 
