In the great Plover (_Œdicnemus crepitans_) the tibia, as in other Grallæ, is longer in proportion to its thickness than in _Didus_; the epicnemial process rises higher above and projects further in front of the condylar surfaces before it divides into the pro- and ectocnemial plates; and these are relatively more produced. The fibular ridge is shorter in proportion to the length of the tibia, is more prominent, and more parallel with the axis of the shaft. The distal condyles project further backward than in _Didus_. The tibia in _Charadrius_, _Otis_, _Tantalus_, _Grus_, _Ciconia_, _Mycteria_, _Porphyrio_, opposes similar or equivalent differences to those in _Œdicnemus_, against the affinity of _Didus_ to any of those Grallæ. In the comparison of the tibia of this extinct flightless bird with that of the _Cnemiornis_, the wonderful development of the plates and processes at the proximal end of the bones in the New Zealand bird is strikingly manifested. In _Cnemiornis_ the fibular ridge runs in a line with the shaft, and does not incline from above obliquely forward as in _Didus_ and the Doves; the ridge on the outer side of the distal fourth of the bone is stronger and sharper in _Cnemiornis_; the tendinal canal is transversely elliptical, medial in position, with a slight inward inclination; the intercondyloid fossa is much wider in _Cnemiornis_. The differences, indeed, in all the characters of the tibia, as compared with _Didus_, in the Vultures, Plovers, Penguins, and terrestrial flightless birds tend to render more instructive and convincing the resemblances which Pigeons present in the same characters to the extinct Mauritian bird. § 4. _Conclusion._ The affinities or place in nature of the Dodo being thus determined by the characters of its skeleton, but few words remain to be said on the bearings of present knowledge of this species upon other zoological generalizations. The researches and observations of naturalists have been carried out to such an extent as to support the conclusion that the _Didus ineptus_ does not now live in any part of the world, and that it never existed save in that part of which the island of Mauritius may be a remnant. Consequently the species there originated; and the most intelligible conception of its mode of origin is that to which I have alluded in the description of the brain-case (p. 39).