418 ZOOLOGY. 
The genus or sub-genus Sarcophilus is intended for those species the 
body of which is stout; the head short, and very broad ; the tail shorter 
than the body; the pre-molar teeth with the antero-posterior and transverse 
diameter equal, or nearly so. The S. ursinus, from Van Diemen’s Land, 
is the only species known of this section. 
It may be compared to a bear in the general proportions of its body and 
limbs, as well as in the texture of its fur. A fossil species, D. laniarius, 
has been found in the caves of Wellington Valley, and seems to come 
nearer S. ursinus; thus, Sarcophilus would not be exclusively limited to 
Van Diemen’s Land, if it has to contain the fossil species. 
Fam. 2. Dipe.puipa, or opossums, composed of numerous species, gene- 
rally of small size, all of them confined to the American continent. Their 
food consists chiefly of insects ; the largest species may occasionally attack 
reptiles, birds and their eggs. There are ten incisors in the upper jaw 
and eight in the lower, arranged nearly in a semicircle. In the upper 
jaw the two foremost incisors are rather longer than the rest, and are 
generally separated from them by a narrow space. The canines of the 
upper jaw are the largest. We find three pre-molars and four molars in 
each jaw. The feet are five-toed, and plantigrade. The general form of 
most of these animals resembles that of the common rat, but they have 
the muzzle more elongated, and terminated in a distinct, naked snout. 
The prehensile tail is almost always very long, nearly destitute of hair, 
excepting at the root, and covered by a scaly skin. Some Didelphide 
have no pouch, or else one in a very rudimentary state. At first the 
young remain very firmly attached to the nipple, and subsequently are 
carried upon the back of the parent, where they retain their position by 
entwining their tails round that of the mother. The mamme vary in num- 
ber from nine to thirteen. The species live in the hollows of trees, or 
amongst their foliage, where they remain concealed during the daytime, 
becoming active in the night only to procure their food. One species lives 
in water, to which habit the webbed feet correspond. 
The genus Didelphys contains animals without cheek pouches, and in 
which the toes of the feet are free. It may be divided into two sections, 
the first including those opossums in which the marsupial pouch is well 
developed, and the second those in which the pouch is rudimentary or 
entirely wanting. 
To the first section belongs the Virginia opossum (D. virginiana), pecu- 
liar to North America, together with the Californian opossum and some 
Brazilian species ; the second chiefly includes species from South America. 
A fossil Didelphys (D. cuvieri) was discovered in the eocene of Paris. A 
few fragments have been found in European other localities. But the 
caverns of Brazil have already yielded six or more, which resemble very 
much those now living in the same country. There is, however, an excep- 
tion: some fragments seem to indicate a new genus, according to the 
researches of Mr. Lund, a Danish naturalist. This, however, has not yet 
been named. 
The genus Chironectes contains but one species, the water opossum 
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