CHAPTER VI. 



Apes, Monkeys, and Lemurs, — continued. 



The Marmosets. 



Family Hapalid.^. 



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. 

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

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

 the American monkeys (Cehidce), yet differ in so many others as to render it necessary 

 to refer them to a distinct family. 



The most important point by wliich 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-si.x 

 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. tliirty-two. If, however, we carefully compare the cheek- 

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

 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 

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

 marmoset 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. Altliough, 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 nundDer of premolars it resendjles 

 an American monkey, from whicli it differs by the comparatively unimjiortant 

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

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

 the dentition of the.se animals maybe expressed by the formula i%, c\,p^,m%; 

 total m. 



The next most impurtaut feature iu wliieli the marmosets differ from tlie true 

 American monkeys is tliat, 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 

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

 allying them to the lower types of Mammals. It is in this group, moreover, that 



