THE MAGAZINE 



OF 



NATURAL HISTOUY, 



SEPTEMBER, 1837. 



Art. I. Observations on the opposable Power of the Thumb in cer- 

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

 natural Affinities which subsist between the Bimana, Quadriimana, 

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

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



It was whilst employed in watching the habits of two fine 

 specimens of Mycetes seniculus in the summer of 1829, that 

 I had occasion, for the first time, to make an observation 

 which greatly surprised me at the moment, and which I 

 afterwards found to be of much greater importance than I 

 had at first imagined. Upon presenting these Mycetes with 

 a few nuts which I had taken for that purpose, I remarked 

 with some surprise that they did not hold them between the 

 finger and thumb, as I had seen other Quadrumana do. 

 This induced me to examine them more closely; and it was 

 with increased surprise and astonishment that I perceived the 

 cause of the phenomenon which had first attracted my 

 attention: the thumb, in fact, though perfectly developed, 

 and, comparatively speaking, much longer than in the 

 ordinary Simiae, was not opposable to the other fingers, but 

 originated in the same line with them ; was of the same long 

 slender form, and acted in the same direction. At first, I was 

 disposed to regard the specimens before me as the type of a 

 new and undescribed genus ; for at that time I had not the 

 slightest suspicion of this character being common to the 

 other Mycetes, much less to the whole of the American 

 Simiadae ; since, though I had formerly seen, and, as I 

 fancied, examined, many of these animals, the observation had 



* This memoir was read before the Zoological Society, March 8. 1S3G, 

 and an abstract from it published in the Proceedings under that date. 

 It is here given verbatim, as it was written, without any alteration or 

 addition, except the foot notes. — W. O. August 10. 1837! 



Vol. I. — No. 9. n. s. l t 



