Before proceeding to the consideration of the distribution of the species, over the different districts of Australasia, it may be remarked that this is a subject surrounded with considerable difficulty, as different naturalists do not always apply the same test to determine the distinction of the species, some considering the differences found in the specimens from different localities, as merely local varieties, and others regarding them as distinct; and others again declaring that several specimens, which cabinet naturalists are in the habit of regarding as only accidental varieties from the examination of the skins, are quite distinct when they are observed alive in their native habitat. In the preceding list, when all the specimens I have seen from a particular habitat have a similar and peculiar character, I have considered them as species; on the contrary when the specimens from the same locality offer variations among themselves, as in those of the genus Hepoona, where the extent of the whiteness on the tail, and the variation in the colour of the body appear to differ in the specimens from the same place, I have regarded them as belonging to the same species, believing it to be a variable species which has an extensive range. From the Table already given it appears that, of the species found on the Australian Continent, 71 are confined to it, 12 common to it and Van Diemen's Land, and one common to it and Norfolk Island; while of the 24 species found on Van Diemen's Land, 11 are found in it alone. The species common to the Australian Continent and Van Diemen's Land, are: 2. Nyctophilus geoffroyii. 4. Scotophilus gouldii. 5. Scotophilus australis. 15. Dasyurus viverrinus. 27. Perameles obesula. 32. Phalangista vulpina. 38. Hepoona cookii. 70. Hypsiprymnus minor. 81. Hydromys chrysogaster. 84. Mus lutreola. 94. Platypus anatinus. The species common to Australia and Norfolk Island, but not found in Van Diemen's Land is: 44. Petaurus sciureus. The eleven species peculiar to Van Diemen's Land, are: 11. Thylacinus cynocephalus. 12. Diabolus ursinus. 13. Dasyurus maculatus. 17. Phascogale minima. 18. Phascogale affinis. 37. Dromicia nana. 34. Phalangista fuliginosa. 58. Halmaturus billardieri. 80. Phascolomys ursina. 93. Echidna setosa. 83. Mus setifer. The last species is also found in Java, from whence it might have been introduced. It has been known in Van Diemen's Land some years, and does not appear to have found its way to Australia. Of the 72 species found in the Australian continent six have only been recorded as having been found on the North-west coast: 52. Macropus unguifer. 55. Halmaturus bennettii. 65. Halmaturus fasciatus. 67. Petrogale brachyotis. 71. Hypsiprymnus lesueurii. Peculiar to the Western Australian district are: 22. Phascogale leucogaster. 23. Myrmecobius fasciatus. 28. Perameles fuscoventer. 29. Perameles obesula. 30. Perameles lagotis. 51. Macropus lunatus.