196 



THE MARSUPIALS. 



directed inwards. In the lower jaw the molars 



have each a sharp cusp in the middle with 



two sharp-pointed side-lobes 



The dental formula is 



teeth. 



The Yapock (Cheironectes variegatus), fig. 



4 • 1 • 3 • 4 



4 = 5o 



rhe Yapock (Cheironectes variegatus). 



248, is the sole representative of its genus, a 

 genus which, as we have already mentioned, 

 is characterized by its aquatic habits and the 

 structure of its hind-feet, in which the long 

 toes are connected by a web reaching to the 

 claws. The first digit is opposable and carries 

 no claw. The claws of the fore-feet are 

 pretty large and sharp. 



The head of this pretty creature, which 

 attains the size of a large rat, is tolerably 

 round ; the ears are of moderate size, and the 

 long round tail is haired only at the root, 

 elsewhere scaly and only sparsely set with 

 bristles. The hair is very soft, silky, and 

 fine; on the back, round the eyes, and on the 

 muzzle of a chestnut-brown colour, on the 

 sides silver-gray, and on the belly white. 

 The throat also is white, and a light stripe 



extends thence to above the eyes, and taper- 

 ing stripes of brown run from the back to 

 mingle with the gray of the flanks. 



The animal is a native of the whole of 

 South America, living on the banks of forest 

 rivers. It is nocturnal in its mode of life; 

 conceals itself by day in holes, feeds on fish, 

 and sometimes gets caught in the nets of 

 fishermen. The female has a complete pouch, 

 which, it may be observed in passing, refutes 

 the theory advanced by some naturalists that 

 the pouch is due to the adaptation of the 

 members of this order to life in arid regions. 

 How could an animal which leads a thoroughly 

 aquatic life possess a pouch if this feature 

 owed its origin to a mode of life directly 

 opposite? 



As a representative of the terrestrial mem- 

 bers of this family forming the genus Didelphys 

 an illustration is given of the Common Opos- 

 sum (Didelpkys virginiand), fig. 249, the 

 animal so much detested by the Americans. 

 This is the largest species of its genus, which 

 has been divided into several sub-genera. 

 These sub-genera are distinguished either by 

 having an imperfect pouch, by having, for 

 example, instead of the pouch merely two 

 folds of skin, as in the sub-genus Philander, 

 or by having a short, naked, and scaly tail, 

 this appendage being in most forms, as in the 

 species now under consideration, capable of 

 being coiled up. This animal is distributed 

 over the whole of North America from Mexico 

 to Canada. Its body attains a length of about 

 20 inches and its tail is about equally long. 



This hateful stinkard has a very sharp- 

 pointed head and uncommonly large ears. 

 The body and neck are strongly built; the 

 hair is thin and soft, the usual colour a fallow- 

 gray, rather darker on the back than on the 

 under parts. 



Like all the members of the genus to which 

 it belongs the opossum leads a nocturnal 

 solitary life. It is a very good climber, em- 

 ploying in climbing principally its fore-paws 

 and its long tail, by the latter of which it often 



