Avoiding the use of denominations, which can only be applied to the monkey, baboon, or ape, we have endeavoured to indicate the sapajous and the sagoins by the names they bear in their native country. We are acquainted with six or seven species of sapajous, and six of the sagoins, most of which have varieties. We have carefully searched after their names in all authors, and particularly in the writings of observant travellers who have first mentioned them, because, in general, the names which any one of them have in their native country is derived from some particular character, which alone was sufficient to distinguish it from all the rest. With respect to the varieties, which in this class of animals are, perhaps, more numerous than the species, we have endeavoured to refer each to its respective species. We have had in our possession forty of these animals alive, differing from each other in a greater or less degree, and from a particular and attentive examination of which, we think the whole may be reduced to thirty species, viz. three apes, and one intermediate species between them and the baboons; three baboons, and one intermediate species between them and the monkeys; nine monkeys, seven sapajous, and six sagoins; the rest, or at least the greatest part of them, ought to be considered only as varieties. But as we are not absolutely certain that some of these varieties may not be distinct species, we shall endeavour to give all of them proper denominations. Here, then, let us consider terrestrial animals, some of which so greatly resemble the human form, in a new point of view. The affixing the name of _quadruped_ to all these animals has been done unjustly. If the exceptions were few we should not have objected to the application of this term. We are convinced that our definitions and names, however general, do not comprehend the whole; that there exists particular beings, which escape the most cautious definitions, and that intermediate species are constantly discovered. We know that many, though to all appearance holding the middle station, have escaped enumeration, and that the general names under which they are included is incomplete; because Nature should never be considered in the aggregate, but by unities only, because man has invented general names only to assist his memory, and because he afterwards weakly regarded those general names as realities; in short, because he has endeavoured to comprehend, under the same denominations, very different animals, and which necessarily required other appellations. I can give both example and proof, without swerving from the class of quadrupeds, which, of all animals, are those best known to man, and to which he was, consequently, the best enabled to give the most precise denominations.