With the exception of the Opossums, which are natives of America, the tribe is peculiar to New Holland and its[157] appendages, and to some of the islands which form the great chain of connexion between that insular continent and South-eastern Asia. The former is, however, their head quarters, and the species which are found beyond its limits are few in number compared with those which people its territory, and, what is more remarkable, people it to the exclusion of nearly all the other Mammalia; the dog alone, the universal concomitant of man, and one or two species of rats, disputing with them their title to its exclusive possession; for those paradoxical creatures, the Ornithorhynchus and Echidna, if really mammiferous, approximate closely in structure to the Marsupial tribe.