452 



ANIMALS OF EGA 



on the surface of our globe, became separated pretty 

 nearly as they now are, soon after the first forms of this 

 group of animals came into existence : it will be inter- 

 esting, therefore, to see how differently the subsequent 

 creations of species have proceeded in each of the separ- 

 ated 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 zoolo- 

 gists. 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 present 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 hemisphere. One of the two 

 American families (Cebidae) has thirty-six teeth, whilst 

 the corresponding family (Pithecidae) of Old World apes 

 has, like man, only thirty-two teeth ; the difference 

 arising from the Cebidse having an additional false molar 

 tooth 1 to each side of both jaws. This important char- 

 acter is constant throughout all the varied forms of which 

 the Cebidae family is composed ; being equally present 

 in the prehensile- tailed group, with its four genera con- 

 taining twenty-seven species, differing in form and 

 clothing, shape of claws, mental characteristics, and con- 

 dition 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 furred and long-haired apes, apes with excessively 

 long tails, and apes with rudimentary tails. The second 

 American family, the Marmosets, have thirty-two teeth, 

 like the Old World monkeys and man ; but this identity 

 of number arises from one of the true molars being absent ; 

 the Marmosets have three premolar teeth, like the Cebidse, 

 and are therefore quite as far removed as the Cebidae 

 from all the forms of the Old World. They are, moreover, 

 a low type of apes, having a smooth brain, and claws 

 instead of nails, although they are gentle and playful in 



^ False molars, or premolars, differ from true molars, through 

 being preceded in growth by milk teeth. 



