496 MANUAL OF ZOOLOGY. 



The fore-limbs have really five toes each, but only the central 

 three of these are well developed, the outermost and innermost 

 digits being rudimentary. The three functional toes are armed 

 with long strong claws, with which the Bandicoots burrow with 

 great ease. The marsupial pouch and this is a singular 

 point opens, in some species at any rate, backwards instead 

 of forwards. In the nearly-allied genus Chczropus, also from 

 Australia, it appears that the two outer toes of the fore-feet are 

 entirely absent. 



The second family of this section namely, the true Opos- 

 sums or Didelphidcz is remarkable in being the only group of 

 the whole order which occurs out of the Australian province. 

 The DiddphidcR) namely, are exclusively found in North 

 and South America, where they are known as " Opossums." 

 A considerable number of species are known, but they are 

 mostly of small size, the largest measuring not more than from 

 two to three feet, inclusive of the tail. The Virginian Opos- 

 sum (Diddphys Virginiana) is the only member of the family 

 which is found in North America, and it was the earliest Mar- 

 supial known to science. Most of the Opossums are carnivor- 

 ous, feeding upon small quadrupeds and birds, but they also 

 eat insects, and sometimes even fruit. One species (Diddphys 

 cancrivora) lives chiefly upon Crabs ; and the Yapock ( Cheiro- 

 nectes] has webbed feet, and appears to lead a semi-aquatic life. 

 All the Didelphidce, have the hallux nail-less and opposable to 

 the other toes, so as to convert the hind-feet into prehensile 

 hands, and all have a more or less perfectly prehensile tail, 

 these being adaptations to an arboreal life. The marsupial 

 pouch is sometimes not present in a complete form, but is 

 merely represented by cutaneous folds of the abdomen con- 

 cealing the nipples. In the Didelphys dorsigera, in which this 

 peculiarity obtains, the young soon leave the nipples, and are 

 then carried about on the back of the mother, to whom they 

 cling by twining their prehensile tails round hers. The dentition 

 of the Opossums is remarkable for the great number of the 

 incisor teeth, the dental formula being 



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 44 i i 33 44 



The Banded Ant-eater (Myrmecobius fasciatiis] is a small but 

 extremely elegant little animal, which inhabits Western and 

 Southern Australia, and lives upon insects (fig. 189). The tail 

 is bushy, and differs from that of the Diddphida in not being 

 prehensile. The fore-feet have five toes armed with claws ; the 

 hind-feet have only four toes. The Myrmecobius is remarkable 



