Chap. V. 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 Cebidse 

 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. 



