In the Doves of flight the proportions and relative position of the three compartments of the cranial cavity differ from those in the Dodo. Both the pros- and mes-encephalic ones are proportionally larger than the epencephalic; and the mesencephalic compartment lies more directly below the prosencephalic one. A very thin stratum of finely cellular diploë divides the two tables of the skull along the medial line of the upper surface: it is thicker between the orbits. The falcial ridge at the inner surface of the prosencephalic roof resembles that in _Didus_. The tentorial ridge bifurcates halfway down, the front portion dividing, almost horizontally, the pros- from the mesencephalic compartment, the hinder and more obtuse ridge dividing, almost vertically, the mes- from the epencephalic compartment. The angle of bifurcation is slightly produced and obtuse, but represents very feebly the tentorial tuberosity (Pl. XI. fig. 1, _o_) in the Dodo: from it, in _Goura_, is continued backward the arch of bone formed by the superior semicircular canal, above which is the groove for the venous sinus, as in _Didus_. The internal auditory fossa is less deep than in _Didus_: above it is a similarly vertically oblong cerebellar pit. The nerve-foramina correspond with those in _Didus_: the entocarotid canal opens into a rather deeper sella in _Columba palumbus_. On comparing the cranial cavity, as exposed by a vertical longitudinal section in the Dodo (Pl. XI. fig. 1), with that of a Dinornis similarly exposed[36], the first difference is the smaller proportional depth of the diploë in the larger wingless bird, which is not greater over the prosencephalic than over the epencephalic compartment; next may be noticed the larger relative size of the former compartment, indicating the larger cerebrum of the Dinornis, then the absence of the tentorial tuberosity, the sharper and more produced superior part of the tentorial ridge arching transversely between the cerebrum and cerebellum, the smaller internal auditory fossa, and the deeper sella: the mesencephalic compartment, or cavity for the optic lobe, is less in proportion to the prosencephalic compartment than in _Didus_; it holds, however, a similar relative position: finally, the cerebellar pit, above the internal auditory fossa, is wanting in the Dinornis. The Dodo agrees with the Doves in possessing a slender furculum, forming an acute angle: it resembles _Columba galeata_, more especially, in the halves of that bone being united by ligament below, and forming separate styles or “clavicles.”