OPOSSUMS. 



281 



appearance of a sixth digit. This animal ranges from Guatemala to Brazil, and 

 is distinguished by its peculiar coloration and aquatic habits. The fur is short and 

 close, and the long tail naked and scaly for the greater part of its length. The head 

 and body measure about 1-i inches in length, and the tail about 15^ inches. The 

 ground-colour of the fur is light grey, upon which there is a blackish brown stripe 

 running down the middle of the back, and expanding into large blotches on the 

 .shoulders, the middle of the back, the loins, and rump. The face has also blackish 

 markings, with an imperfect whitish crescent above the eyes; while there is a 



water-oposscm (J nat. size). 



certain amount of the dark tint on the outer surfaces of the limbs, the under-parts 

 being pure white. The female possesses a complete pouch. In habits the yapock 

 closely resembles an otter, to which group of animals it was indeed referred by the 

 earlier naturalists. Its food consists of crustaceans, small fish, and other aquatic 

 animals. 



Extinct Marsupials. 



From their low degree of organisation it would be expected that Marsupials 

 are some of the oldest of mammals; and this expectation is borne out by the 

 facts. So far as can be determined, no placental mammals are known to have 



