CHAPTER VI 



APES, MONKEYS, AND LEMURS continued 



THE MARMOSETS 

 Family 



THE last, and at the same time the smallest, of all the true Primates are the 

 tiny and beautiful little creatures popularly known as marmosets and tamarins. 

 These elegant little animals, many of which are much smaller than a squirrel, are 

 confined to South and Central America, and, although agreeing in many points with 

 the American monkeys ( Cebidcz) , yet differ in so many others as to render it neces- 

 sary to refer them to a distinct family. 



The most important point by which the marmosets are distinguished from the 

 American monkeys relates to their teeth. It will be remembered that the American 

 monkeys are distinguished from all their Old World cousins by having thirty-six 

 in place of thirty-two teeth ; the increase being due to the presence of an additional 

 bicuspid or premolar on either side of each jaw. Now, if we take the skull of a 

 marmoset and count its teeth, we shall find that their number is the same as in the 

 Old World monkeys, viz. , thirty-two. If, however, we carefully compare the cheek- 

 teeth with those of an Old World monkey, we shall find that there is a very 

 important point of difference. Thus, whereas in an Old World monkey, there are 

 on each side of both the upper and the lower jaw two bicuspids or premolars (teeth 

 which are preceded by milk-teeth) and three molars, we shall find that in our 

 marmos * there are three premolars and only two molars. That is to say, in place 

 of there being two cheek-teeth with a pair of cusps on the crown, which are pre- 

 ceded by milk-teeth, and three teeth with four cusps which are not so preceded, 

 there are three of the former type and only two of the latter. Although, then, a 

 marmoset agrees with an Old World monkey in the total number of its teeth, yet 

 in the much more important character of the number of premolars it resembles 

 an American monkey, from which it differs by the comparatively unimportant 

 feature of the loss of the last molar in each jaw. A marmoset may, indeed, be 

 defined as a small American monkey which has lost its wisdom teeth; and 

 the dentition of these animals may be expressed by the formula z'f, c{, /f, m\\ 

 total 32. 



The next most important feature in which the marmosets differ from the true 



America monkeys is that, with the exception of the great toe, all their fingers and 



toes are furnished with pointed claws, instead of more or less flattened nails ; this 



character, like the presence of the additional premolar tooth in each jaw, clearly 



(188) 



