III.] MONKEYS. 69 



With these preliminary considerations, we pass to a critical 

 examination of the recent and fossil mammalian fauna of Neogaea, 

 which will show how intimately investigations of this nature are 

 connected with the present and past configuration of the land- 

 areas of the globe. 



Like as are many of them superficially to their cousins of the 

 Old World, the monkeys of the New World, which 



,, , , .... . - Monkeys. 



are now confined to the tropical forest-regions of 

 the Neogaeic realm, are structurally quite different to the former ; 

 and this circumstance, coupled with their isolated distribution, in- 

 dicates that their relationship is, at most, but a very distant one. 

 Indeed it is not improbable that the Old and New World monkeys 

 may have originated independently from the group of lemurs, which 

 were formerly very widely distributed over Arctogaea. Of the 

 two families of Neotropical monkeys, the first is represented by 

 the beautiful little marmosets, constituting the family Hapalida. 

 Although having the same number (32) of teeth as the Old World 

 monkeys, the marmosets differ in that the number of premolars on 

 each side of both jaws is three, and that of the molars two ; these 

 numbers being transposed in the other group. The marmosets 

 are further distinguished by the broad septum between the nostrils, 

 the absence both of pouches in the cheeks and of callosities on 

 the buttocks, and the want of any prehensile power in the tail ; in 

 addition to which it may be noticed that the thumb is not op- 

 posable to the other fingers, while all the digits, with the 

 exception of the first on the hind foot, are provided with long 

 claws. None of these animals are known from the Santa Cruz 



FlG. 9. PART OF RIGHT LOWER JAW OF HoniUHCulus. 



deposits. In the second family or Cebidce, which includes much 

 larger species than the diminutive marmosets, the total number of 



