﻿196 Allen's naturalist's library. 



wing-cases of Beetles. In their large number of incisor teeth 

 — live pairs in the upper, and four in the lower jaw — the 

 Opossums, as shown in the figure on page 129, differ from all 

 other Mammals, the Peramclidce coming next to them in this 

 respect, with, at most, five pairs in the upper, and three in the 

 lower jaw. These teeth are arranged in each jaw nearly in the 

 form of a semicircle ; in the upper jaw the inner pair are 

 somewhat longer than the rest, from the nearest of which they 

 are generally separated by a narrow interval, their form being 

 nearly cylindrical, with a slight dihtation at the summit. The 

 canine teeth are well-developed, those of the upper jaw being 

 somewhat longer than those opposed to them. 



In general form and appearance the majority of Opossums 

 may be compared to the common Grey Rat, except that the 

 muzzle is more elongated, and completely naked at the extremity, 

 where it is perforated by the nostrils. In the larger species the 

 form of the body is proportionately stouter. A peculiarity of 

 the Opossums is that the teats, which are always numerous, 

 varying from five to twenty-five, are always an odd number ; 

 either a single odd one, or as many as five being placed in the 

 centre of a circle or oval formed by the others. 



In the case of the short-tailed group, forming the sub-genus 

 Feramys, the series of specimens available to the author of the 

 British Museum Catalogue of Marsupials was insufficient to 

 allow of the proper determination of all the species, which may 

 consequently stand in need of revision. 



THE TRUE OPOSSUMS. GENUS DIDELPHYS. 

 Didelphys^ Linn., Syst. Nat., ed. 10, vol. i., p. 54 (1760). 



I. COMMON OPOSSUM. DIDELPHYS MARSUPIALIS. 



Didelphys viarsiipialis, Linn., Syst. Nat., ed. 10, vol. i., p. 54 

 (1760); Thomas, Cat. Marsup. Brit. Mus. p. 323 (1888;. 



