MAMMALIA 321 



is reduced. The corpus callosum, if present, is rudimenatry. 

 Parameles possess a true allantoic placenta. Many thousand 

 skins of the opossums are used yearly. The hair is used in 

 making hats and felt. The fur and leather of the kangaroo 

 are also used. 



The opossum family (Didel'phidoe) consists of pendactylous, plantigrade 

 marsupials. The pouch is present or absent according to the species. The 

 great toe is large and separable from the others, making the foot prehensile. 

 The tail is long, prehensile, and usually covered by a scalj' skin and a few- 

 scattered hairs. There are two distinct genera. The first has been divided 

 into several by some authors. 



Fig. 263. — The female of Didel'phys dorsig'cra, one of the South American 

 opossums, carrying its young upon its back. (After Nicholson.) 



Genus Didelphys comprises twenty-three species, most of which are 

 tropical, being found in Mexico, Central America, and Brazil, but never in 

 Australia. It is represented in the United States by the common opossum 

 {Didel'phus Virginia' na) . Its habit of feigning death or "playing 'possum " 

 when confronted by an enemy is well known. It is about the size of a 

 large cat. Its nose is pointed, its eyes and ears large. It is arboreal and 

 nocturnal. It eats anything from insects to small reptiles and birds, and 

 also devours muskmelons and certain mushrooms; indeed, it is almost 

 omnivorous. It does not hibernate. Its young are about J inch in length 

 and are carried in the pouch for about eight weeks. After this, in some 

 species, they are carried on the back (Fig. 263), their tails interlocking 

 with that of the mother. 



Tasmanian marsupials (family Dasyur'idoe) are distinguished from the 

 American opossum by fewer incisor teeth, a rudimentary first digit on the 

 fore and hind feet, by the absence of a cecum, and by a non-prehensile tail. 



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