considered as a zoological Character. 45 1 



of all the natural genera, I am now able to announce with 

 confidence that the American Simiadae have not the thumb of 

 the anterior extremities opposable to the other fingers ; in short, 

 that they are not Quadrumana, and, consequently, that any 

 zoological system which includes them in the same group 

 with the Simiae of Asia and Africa is founded upon arbitrary 

 principles, and opposed to the observed phenomena of their 

 structure and economy. 



When I first made the observation which led to this 

 important conclusion, I was anxious, as may be readily 

 supposed, to examine strictly the works of the most original 

 and trustworthy writers upon this subject, for the purpose of 

 ascertaining whether the fact might not have been already 

 recorded, though it had been overlooked by subsequent 

 authors. A strict and attentive search, however, convinced 

 me that the observation had not been made by Linnaeus, 

 Buffon, Pennant, Erxleben, Illiger, Geoffroy St. Hilaire, the 

 Cuviers, Desmarest, Humboldt, nor even by the accurate and 

 minute Daubenton. So close, indeed, is the approximation 

 of the American to the Asiatic and African animals in general 

 form and manners, that these illustrious naturalists seem 

 never to have thought of comparing them in the more minute 

 details of their conformation ; nor, for that matter, should I 

 have myself ever dreamed of the American Simiadae differ- 

 ing in this respect from the Simiae of the Old World, 

 had not chance thrown the observation in my way, in the 

 manner already mentioned. At that time I did not possess 

 Azara's admirable Essais snr VHistoire Naturelle des Qua- 

 drupedes de la Province du Paraguay ; nor, for long after I 

 procured it, did I think of consulting it upon this subject. 

 When I did so at length (and it was only when about to 

 prepare the present memoir), it was with the greatest 

 pleasure I discovered that that acute and original observer 

 had long since made the very same remarks which for- 

 merly struck me with so much surprise; and I hailed the 

 circumstance as a complete confirmation of the correctness 

 of my own observations. Since, then, the credit of having 

 been the first to make this important observation is due to 

 the Spanish naturalist alone, I shall transcribe the following 

 short extracts from his work, in order at once to establish his 

 claim to the original discovery, and to bring forward his 

 authority in support of the observation itself. 



Speaking of the caraya (Mycetes niger), Azara says : — " La 

 main a cinq doigts, dans lesquels celui qui par sa position doit 

 etre le pouce ne semble pas tel, attenduqu'il nait sur la nieme 

 Jigne que les autres, qu'il a la meme direction, et qu'il est le 



