5. The Nearctic Region; including Greenland, and N. America, to Northern Mexico. 6. The Neotropical Region; including South America, the Antilles, and Southern Mexico. This division of the earth received great support from Dr. Günther, who, in the _Proceedings of the Zoological Society_ for 1858, showed that the geographical distribution of Reptiles agreed with it very closely, the principal difference being that the reptiles of Japan have a more Indian character than the birds, this being especially the case with the snakes. In the volume for 1868 of the same work, Professor Huxley discusses at considerable length the primary and secondary zoological divisions of the earth. He gives reasons for thinking that the most radical primary division, both as regards birds and mammals, is into a Northern and Southern hemisphere (Arctogæa and Notogæa), the former, however, embracing all Africa, while the latter includes only Australasia and the Neotropical or Austro-Columbian region. Mr. Sclater had grouped his regions primarily into Palæogæa and Neogæa, the Old and New Worlds of geographers; a division which strikingly accords with the distribution of the passerine birds, but not so well with that of mammalia or reptiles. Professor Huxley points out that the Nearctic, Palæarctic, Indian, and Ethiopian regions of Mr. Sclater have a much greater resemblance to each other than any one of them has to Australia or to South America; and he further suggests that New Zealand alone has peculiarities which might entitle it to rank as a primary region {60}along with Australasia and South America; and that a Circumpolar Province might be conveniently recognised as of equal rank with the Palæarctic and Nearctic provinces. In 1866, Mr. Andrew Murray published a large and copiously illustrated volume on the _Geographical Distribution of Mammals_, in which he maintains that the great and primary mammalian regions are only four: 1st. The Palæarctic region of Mr. Sclater, extended to include the Sahara and Nubia; 2nd. the Indo-African region, including the Indian and Ethiopian regions of Mr. Sclater; 3rd. the Australian region (unaltered); 4th. the American region, including both North and South America. These are the regions as _described_ by Mr. Murray, but his coloured map of "Great Mammalian Regions" shows all Arctic America to a little south of the Isothermal of 32° Fahr. as forming with Europe and North Asia one great region.