We have now only to examine the nomenclature of Linnæus, which in this article is much less erroneous than in many others, for he suppresses one of the three species of Seba; but he should have reduced them to one. Besides, he employs the distinctive character of the toes behind without claws, which none but Tyson had observed. The description which Linnæus gives of the opossum as the _marsupialis_, seems to be a good one, and agreeable to Nature, but he is in an error when under the name of opossum he designs an animal different from his _marsupialis_, upon the authority of Seba, acknowledging, however, that this opossum had no claws to the toes behind, whilst they are very visible in the figures of Seba. Another error is, considering the _maritacaca_ of Piso, as the same animal as the _carigueya_, whilst these two animals, though mentioned in the same chapter, are mentioned by Piso as two different animals, and he describes them one after the other. But his greatest error is in making two different species of the _marsupialis_ and the opossum; they have both, according to Linnæus, the pouch, the hind toes of their hind feet have no claws, are both natives of America, and only differ in this respect, by the first having eight paps, and the second only two, and the spot above the eyes more pale. These characteristics cannot be sufficient to distinguish them as distinct species; for the first can scarcely be called a difference; nor can any thing be established as fixed or certain, in regard to the order and the number of the paps, since they vary in the same species of most animals.