Opjjosable Power of the Thumb. 5 1 7 



Art. III. Observations on the opposable Power of the Thumb in 

 certain Mammals, considered as a zoological Character; and on the 

 natural Affinities which subsist between the Bimana, Quadrumana, 

 and Pedimana. By W. Ogilby, Esq., M.A., FX.S., F.G.S., 

 F.Z.S., &c. &c. 



{Concluded from p. 459.) 



Having thus got a group of Pedimana, consisting, as in the 

 Quadrumana, of two distinct families, I proceed, in the third 

 place, to develope the relations which subsist between these 

 minor groups; and to show, in the fourth place, that the 

 Didelphidae form, in some measure, a parallel chain to the 

 Lemuridae, as I have already shown that the Simiadae do to 

 the Simiae.* Now, it must be observed, once for all, that 

 there is no gradual transition of character, no intermediate 

 forms, to connect by imperceptible gradations the extreme 

 links of the Quadrumana and Pedimana, nor even to unite 

 the two minor groups of which I have shown that these 

 families are respectively composed. The Lemuridae are as 

 distinct from the Simiae as the Didelphidae are from the Simi- 

 adae, in some of their most remarkable and influential charac- 

 ters ; but there are, nevertheless, other relations, besides those 



* It was only within the last few days that I accidentally happened to 

 meet with a passage in the Histoire Naturelle which shows that these 

 relations had occurred to, and made a strong impression upon the mind 

 of, the great Buffon ; a philosopher who, had he not been unfortunately 

 biassed against all system, would have probably given us a more correct 

 arrangement of mammals than any which has yet appeared. The little 

 that he attempted of this nature is almost perfect in its kind, and has 

 never since been departed from. He was the first to introduce anything 

 like order or generic distinctions among the Simiae and Simiadae, and 

 more particularly to distinguish these two groups from one another ; he 

 appears, indeed, to have made an especial study of the relations of all of 

 these animals; and it is not a little singular, that, with the extremely imper- 

 fect materials which he possessed, he should have arrived at the same 

 results to which I have been myself conducted by a much more extended 

 range of observations. In fact, he only knew the most distant extremes 

 of the groups ; the Lemurs proper and Indris among the Lemuridae, and 

 the single genus of Opossums among the Didelphidae : of the connecting 

 links which fill up the chasm he was only acquainted with one species of 

 Balantia. His words are : — " Cependant comme les Singes, les Babouins, et 

 les Guenons ne se trouvent que dans l'ancien continent, on doit regarder 

 les Sapajous et les Sagoins comme leurs representans dans le nouveau ; 

 car ces animaux ont a peu pres la meme forme, tant a I'exterieur qu' a 

 Pinterieur, et ils ont aussi beaucoup de choses communes dans leurs habi- 

 tudes naturelles : il en est de meme des Makis, dont aucune espece ne 

 s'est trouvee en Amerique, et qui neanmoins paraissent y etre remplaces 

 ou representees par les Philandres, c'est a dire par les Sarigues, Marmoses, 

 et autres Quadrumanes a museau pointu, qui se trouvent en grand nombre 

 dans le nouveau continent, et nulle part dans Pancien." (Hist. Nat., 

 4to edit., xiv. 368.) — W. O. August 10. 1837. 



