3 8o TROPICAL AMERICA AND ITS ANIMALS 



Although, as already stated, North America has but one or two 

 marsupials, in South America the order is well represented. The 

 opossums of the area under consideration are, however, much smaller than the 

 common species of the north, of which local races are met with. One of the 

 South American opossums found in Guiana and in southern Brazil and Argentina 

 is the thick-tailed opossum (Didelphys crassicaudata), distinguished by the tail 

 being thickly haired along its basal half and thinly haired almost to the tip. 

 As in the rat-tailed opossum (D. nudicaudata), which ranges from Costa Rica to 

 Brazil, its pouch is rudimentary or absent. Unlike the latter, the Quica opossum 

 (D. opossum) has a tail bare of hair except at the base, and a well-developed pouch. 

 All three are of medium size with long tails and short crisp fur. On the other 

 hand, in the philander opossum (D. philander) of Guiana and north-eastern Brazil, 

 the fur is woolly and soft. Another species, ranging from Mexico to Paraguay, is 

 the woolly opossum (D. lanigera), which is of somewhat larger size and is the 

 common opossum of tropical South America. Neither species has a pouch, the place 

 of which is taken by two large folds on the skin, and consequently the females have 

 to carry their young, sometimes twelve in number, on their backs, a load which does 

 not hinder them from climbing trees with great quickness. The philander opossum 

 is distinguished by a narrow brown line down its pale grey face, and a brown ring 

 round each eye, its general colour being reddish or yellowish grey above and 

 yellowish below. The murine opossum (D. mwrina), which has the dark eye-stripes 

 very noticeable, ranges from central Mexico into Brazil, and somewhat resembles a 

 bright red mouse. Another group of opossums is composed of still smaller species, 

 the smallest being the pigmy opossum (D. sorex) of Rio Grande do Sul, which is 

 less than 3 inches long. It should be added that by many modern zoologists 

 the ai'boreal opossums are divided into several generic groups such as Philander 

 and Marmosa. Whether such subdivisions are altogether advisable may be an 

 open question, but there is no doubt as to the right of the yapock, or water-opossum 

 (Chironectes minima), to rank as a genus by itself. Its range extends from 

 southern Brazil to Guatemala. In colour it is greyish white curiously marked and 

 marbled with dark brown, four broad saddle-like patches extending from the dark 

 line on the back down the sides. In habits and mode of feeding the yapock so 

 closely resembles an otter that it was at first regarded as a diminutive member of 

 that group. In length it measures about 14 or 15 inches. 



Although described in two papers, one written in 1860 and the 

 other in 1863, the marsupials known as selvas long escaped full 

 recognition. In external appearance, and especially in their long, sparsely haired 

 tails, they resemble rats, and have almost rat-like incisors. The larger species 

 (Ccenolestes fuliginosus) is a dark brown animal of the approximate size of a rat, 

 with a small and undeveloped but distinct pouch, and all the habits of an opossum, 

 although not closely related to the latter. This species and its Bogota relative, 

 C. obscurus, were at first referred to the diprotodont section of the marsupial order 

 (see the section on Australia in vol. iii.), but it was subsequently pointed out that 

 they showed so many polyprotodont resemblances as to preclude their reference to 

 the former group, and C. fuliginosus was made the type of a new sub-order, 

 Paucituberculata. Still later, the diprotodont lower dentition (like the front teeth 



