26 



further back than the general line of the other fingers, and has, on 

 that account, when superficially noticed, the semblance of being 

 opposed to them ; but, as has been correctly obsen'ed by D'Azara 

 with reference to Ceb. capucinus, it is less separated than in Man : 

 it is, besides, of precisely the šame slender form ■with the ręst, is 

 weaker than them, absolutely -^-ithout power of opposition to them, 

 and habitually acts in the šame direction -^ith them. The impres- 

 sion derived from contemplating the hands of the 01d World Mon- 

 keys might induce the belief that the extremities of the Cebi are si- 

 milarly constituted : but if the knowledge that in Mycetes, Pithecia, 

 &c., there are no opposable thumbs, lead to a close observation of 

 the anterior extremities of the Cebi, it vnO. be found that they do 

 not act as hands, and cannot be considered as possessing the pow'ers 

 of those organs. From innumerable obser^'ations of many species 

 of that genus Mr. Ogilby statės that it was very e^^dent, notwith- 

 standing the fallacious appearance occasioned by the back'n'ard posi- 

 tion of the organ, that they had not the power of opposing the 

 thumb to the other fingers in the act of prehension : and, in fact, 

 their principai po\ver of prehension seems to be altogether indepen- 

 dent of the thumb, for, generally speaking, that member -^as not 

 brought into action at all, at least not simultaneously with the other 

 fingers, but hung loosely on one side, as Mr. Ogilby has seen it do, 

 in likę circumstances, in the Opossums, Phalangers, and other ar- 

 boreal Mammals : when actually brought into play, however, the 

 thumb of the Cebi invariably acted in the šame direction as the other 

 fingers. Cebus conseąuently agrees in the character of non-oppos- 

 ableness of thumb \\\th. the nearly aUied genera. And in this hi- 

 therto unsuspected peculiarity zoologists obtain a far more impor- 

 tant character by which to distinguish the Monkeys of the 01d and 

 New World than that hitherto relied on, the comparative thickness 

 of the septum narium, or than the accessory aids aiForded by the 

 absence of cheek-pouches and callosities. Hence, according to 

 Mr. Ogilby, as the Monkeys of America have now been ascertained to 

 be destitute of anterior hands, they can be no longer included among 

 the Quadrumana; and he proposes in conseąuence to regard them as 

 Pedimana. He considers that in the latter series, the Monkeys of 

 America form a group parallel to that of the Monkeys of the 01d 

 World among the Quadrumana : and viewing the Quadrumana as 

 consisting of two primary groups, that of which Simia forms the 

 type, and the Lemurida, he j^rocecds to analyse the Pedimana in 

 order to determine whether any group analogous to the Lemurs 

 exists in it. He finds such a group in the association of the genera 

 Didelphis, Cheironectes, Phalangista, Petaurus, and Phascolarctos, 

 (together with a new genus, Pseudochirus, ■vv'hich he has found it 

 necessary to separate from Phalangista as at present constituted) ; 

 and for this association he uses the name of DidelpkidcB. Aware 

 that the modifications observable in the dentary systems of these 

 Severai genera have been regarded by many zoologists as betoken- 

 ing a diiference of regimen, which has led to their being viewed as 

 constituting distinct families ; he, in the first place, statės, as the 



