OF THE UNITED STATES 367 



which are, no doubt, of the greatest use to such a climbing ani- 

 mal as an opossum. On the anterior limbs all the five digits 

 are provided with long sharp claws, and the pollex or thumb is 

 but little opposable. Their numerous teeth are covered with 

 minute sharply pointed cusps, with which to crush the insects 

 on which they feed, for the opossums seem to take in South 

 America the place in the economy of nature filled in other coun- 

 tries by the true Insectivora, the hedgehogs, moles, and shrews. 



" The family consists of two well-recognized genera only, viz., 

 Didelphys, containing all the members of the family, with the ex- 

 ception of the Tapock, a curious animal which forms by itself 

 the second genus, Chironectes, and is distinguished from all other 

 opossums by its webbed feet, non-tuberculated soles, and pecu- 

 liar coloration. Its ground color is light gray, with four or five 

 sharply contrasted brown bands passing across its head and 

 back, giving it a very peculiar mottled appearance. It is almost 

 wholly aquatic in its habits, living on small fish, crustaceans, 

 and other water animals; its range extends from Guatemala to 

 southern Brazil." 



As has already been stated above, the genus Didelphys con- 

 tains all the other forms of opossums, and a very heterogeneous 

 collection they are; D. virginiana or our common Virginia or 

 American opossum being by far the best known representative 

 of the genus. This genus Didelphys could doubtless with truth 

 and propriety be split up into several well-defined genera, each 

 possessing good generic characters. For example, some of the 

 species of opossums are large-sized ones, like our United States 

 form, with coarse, long, dark-colored pelage, big leafy ears, com- 

 pletely developed marsupial pouches, and with distinguishing 

 internal anatomical characters. The Crab-Eating opossum (D. 

 cancrwora) of South and Central America, is another well- 

 known type of this group, and not very unlike the American 

 opossum. 



" The second group, or subgenus, named Metachirus" as re- 

 marked by Thomas, " contains a considerable number of species 

 found all over the tropical parts of the New World. They are of 

 medium size, with short, close fur, very long, scaly, and naked 

 tails, and have less developed ridges on their skulls. They have, 

 as a rule, no pouches in which to carry their young, and the lat- 

 ter therefore commonly ride on their mother's back, holding on 

 by winding their prehensile tails round hers." The Lord Derby's 



