Of the skull of the Dodo, the series of bones transmitted to me include the cranial part with the detached upper mandibular bone (more or less mutilated) of two mature birds, and the lower mandible of three individuals. In the latter the dentary elements (Pl. XI. fig. 1, 32), confluent at the “gonys,” are distinct from the hinder halves of the rami formed by the confluent, or perhaps connate, articular, surangular and angular elements (ib. 31): if the “splenial” were ever distinct, it has coalesced with the dentary, where its upper boundary is indicated by a linear groove or series of small foramina. In size, shape, and all other characters of these important evidences of the specific nature of the remains from the Mahébourg morass[29], they agree with those of _Didus ineptus_ detailed in the ‘Proceedings of the Zoological Society’ for January 11th, 1848 (part xvi. pp. 2–8), and in the work entitled “The Dodo and its Kindred,” pp. 76–96. The occipital condyle (ib. 1) presents the same hemispheroid or reniform shape, with the median vertical notch or depression above. The upper margin of the foramen magnum is broad, as it were excised, with the sides slightly prominent. The superoccipital foramen is present in both specimens, as in the one originally described (Proc. Zool. Soc. part xvi. p. 2). This foramen also exists in Owls and Parrots, but not in all Pigeons; the _Didunculus_ (Pl. III. fig. 2) shows no trace of it; I have also failed to find it in the skull of a Crown-pigeon (_Goura coronata_). The superoccipital ridge is defined by the subsidence of the surface beneath it being continued directly from the upper, almost flat, smooth surface of the cranium: the middle part of the ridge is more produced than the angles. In the great breadth of the occipital surface compared with its depth, in its flatness from side to side, and its aspect backward and a little upward, _Didus_ most resembles _Dinornis_. The basioccipital curves downward, and unites with the basisphenoid in developing the pair of larger tuberosities (Pl. XI. fig. 1, 5), which terminate about ½ an inch below the occipital condyle. There is nothing of this structure in the Columbine cranium. In one of my Dodo’s skulls there is a pair of small tubercles between the larger basioccipital ones; these are not developed in the other cranium. The basisphenoid is subquadrate, and flattish below, impressed by a shallow median longitudinal channel.