452 Opposable Power of the Thitmb 



plus foible. Les pieds ont les memes doigts, mais Pinterne 

 a la forme de pouce." * Again, in describing the cay (Cebus 

 capucinus), he observes : — " II y a cinq doigts a chaque pied, 

 presque de la meme forme que ceux de la main de Phomme, 

 quoique le pouce de devant soit moins separe que dans celui-ci, 

 et qu'il ne soit pas plus gros que les autres doigtsf:" and 

 again, of the mariquoina (Pithecia Mariquoina) : — " Dans la 

 main il y a cinq doigts ; Pextreme et l'interne naissent paral- 

 lelement entre eux, quoique celui-ci soit plus court: il n'a ni 

 la separation ni la forme d'un pouce, et il est le plus mince 

 de tous. Les trois autres doigts sont plus longs que les deux 

 precedens ; ils naissent un peu plus en avant, et leur longueur 

 suit Pordre des doigts de la main de Phomme." % 



These passages clearly establish Azara's title to be con- 

 sidered the original observer of this important fact ; and it is 

 not a little surprising that they should have remained so long 

 buried in his admirable Essais, without having attracted that 

 attention to which they are so justly entitled. Such, however, 

 has hitherto been their fate : subsequent writers seem to have 

 entirely overlooked them, or, if noticed at all, their real value 

 was not appreciated ; nor am I aware of the observation 

 itself having been made by any other naturalist, with the 

 exception of Mr. Martin, an able and zealous officer of the 

 Zoological Society, to whose merit I am happy to have this 

 opportunity of bearing witness. So far as I know, however, 

 Mr. Martin has not followed up the ideas suggested by this 

 observation, nor deduced from it the consequences to which 

 it necessarily leads, and which it is the principal object of the 

 present memoir to develope. § 



I have thought it necessary to enter into this circumstantial 

 history of the observation in question, in justice to all those 

 whom I know to be connected with a discovery which I 

 cannot avoid considering as one of the most important that 

 has been made of late years in mammalogy, more especially 

 in regard to its connexion with the principles of natural 

 classification in this department of zoology. I shall only 

 remark further, that the present memoir, though commenced 

 last November ||, immediately after examining a specimen of 



* Azara, Quad, du Parag., ii. 213. f Id. ii. 233. X Id., ii. 244. 



§ When this passage was written, I had entirely forgotten that I had 

 myself previously published the observation in question, in an article 

 on the " Zoology of America," inserted in the Penny Cyctopcedia y vol. i. 

 p. 442. That article was published in 1833, and Mr. Martin's observ- 

 ations upon the subject did not appear till December, 1835. They may 

 be found in the volume of the Penny Magazine for that year. — W. O. 

 August 10. 1837. 



II 1835. 



