456 Opposable Power of the Thumb 



Simkdae accords precisely with the difference of organic 

 structure already pointed out in these animals ; those which 

 approach most nearly to the true Quadrumana in the con- 

 formation of the organs of touch and prehension, exhibiting, 

 at the same time, a degree of intelligence vastly superior to 

 their conterminous genera. In short, here, as in all other 

 cases, that admirable instrument, the hand, or even an approxi- 

 mation to its form, however imperfect it may be, entails upon 

 its possessor a superior developement both of mental and 

 physical functions, and, exactly in proportion to its degree of 

 perfection, and to its adaptation to the purposes of touch and 

 prehension, exalts him in the scale of animal life. 



But, though the Sapajous and Sagoins of America differ 

 thus essentially from the true quadrumanous types of the 

 Old World, they exhibit, nevertheless, numerous important 

 relations in other respects, more especially with the family of 

 Simiae, which cannot be overlooked, and which, indeed, have 

 hitherto been solely relied upon for determining their position 

 in the scale of nature. Among the Pedimana, in fact, they 

 form a parallel group to the true Simiae among the Quadru- 

 mana ; and it is for the purpose of expressing at once the 

 difference which exists between these two groups, and the 

 relations which they exhibit to one another, that I propose to 

 appropriate the term Simiadae to the American animals, re- 

 serving the name of Simiae exclusively for those of the Old 

 World, to which alone it originally and legitimately belongs. 

 I am ready to acknowledge the impropriety, under ordinary 

 circumstances, of substituting new names in the place of those 

 which have been already received into the science ; the terms 

 Catharhinnius and Platyrhinnius, however, which M. Geof- 

 froy St. Hilaire has already applied to the same groups, be- 

 sides not being generally adopted by other zoologists, express 

 such trivial and unimportant relations, compared with the 

 ideas attached to those which I propose to substitute for them, 

 that the change is in this instance a decided advantage ; nor 

 does it deduct from the merit of the learned professor, since 

 whatever novelty or discovery the case presents is contained 

 in the observations here recorded; and the loss of a mere 

 name is not a circumstance that can affect the solid and well- 

 earned reputation of the illustrious French zoologist. The 

 proposed change has, besides, the farther advantage of rein- 

 troducing into the science the old classical name of a group 

 which has for some time past fallen into neglect, but which is 

 much more appropriate and expressive than any of those by 

 which it has been replaced. 



In the second place, the Sagoins and Sapajous, or, as I 



