The _Dinornithidae_ form a separate group of the order _Ratitae_, in no way closely related to the Australian Emu (_Dromaius_), as many ornithologists have asserted, but nearer to the South American Nandu (_Rhea_) than any other living _Ratitae_, though exhibiting many characters in common with the _Apterygidae_. There have been a number of classifications set up of this family. The first by Reichenbach, in 1850, with 7 species and 7 genera! {187} The next was by Von Haast, in 1873, who enumerated 10 species, divided into 4 genera. The third was Lydekker's, in 1891, who acknowledged 23 species, divided into 5 genera. Then came Hutton's, in 1892, which left out _Megalapteryx_, with its then known 2 species, and acknowledged 26 species, divided into 7 genera. Lastly we have Professor Parker's, in 1895, in which again _Megalapteryx_ is left out, and 21 species are acknowledged, divided into 5 genera. There has been a great amount of controversy as to the number of species of Moas which really ought to be distinguished, and of late years there has been a tendency to unite most of the species as synonyms, the authors declaring that bones vary to such a degree that all the characters relied on for the distinguishing of the various species were individual variations, and that, besides, it was impossible that so many distinct forms could have occurred in such a small area. The extreme of this lumping was reached when Professor Forbes, in the Bulletin of the Liverpool Museums, III, pp. 27 and 28 (1900), divided the Moas into six genera, each with a single species. He thus ignores the fact that by doing so he has united forms which were founded on FULLY ADULT bones, and yet some of them were only about half or two-thirds the size of the others. I personally think that too many species have been made, and at least 7 of Captain Hutton's forms must be sunk. On the other hand some have been described since 1895 and 1900, and I have been obliged to name others rather against my will, so that in spite of uniting so many species of others I find I am obliged to acknowledge more species than anyone else. I have divided these into genera according to Professor Parker's classification, only adding _Palaeocasuarius_ of Forbes, with 3 species, and _Megalapteryx_, with 5, which brings my number up to 38 species, divided into 7 genera. My reasons for not uniting these into 7 species and 7 genera, as those of the "lumping school" do, are twofold,--first, the bones of the _Ratitae_ are much more solid than those of other birds, and are not given to so much individual variation; and, secondly, in the face of the great number of species of Paradise Birds and Cassowaries found on New Guinea, the contention that there could not be so many species of Moa on so small an area is not easily maintained. Moreover, we have strong support in the present fauna and flora for the presumption that, when the Moas first came into existence and differentiated into