OSTEOLOGY OF THE DODO. 77 



of the prosencephalic roof resembles that in Didus. The tentorial ridge bifurcates half- 

 way down, the front portion dividing, almost horizontally, the pros- from the mesen- 

 cephalic 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 (PI. XXIII. 

 hg. 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 Didiis. 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 (PI. XXIII. fig. 1), with that of a Dinornis similarly exposed', the first difierence 

 is the smaller proportional depth of the diploe in the larger A^dngless 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 cere- 

 brum 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 

 cgrebrum 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 posi- 

 tion: 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." 



The humerus of the Goura closely repeats most of the characters described in that of 

 the Dodo ; but its length is proportionally greater, being 3 inches 9 lines, nearly equal to 

 that of the sternum or pelvis, whereas the humerus of the Dodo is little more than half 

 the length of either sternum or pelvis. The processes for the attachment of the muscles 

 are, nevertheless, fully as strongly developed in Didus (PI. XX. figs. 12 «& 14) as in the 

 volant Doves (PI. XXIV. figs. 8 & 9, Goura) ; that, indeed, which is a ridge (r) on the 

 back part of the shaft in Didus, is a mere rough surface in Goura, and does not show 

 in Didunculus. The pneumatic fossa, which varies in depth in the two humeri of the 

 Dodo, is in both relatively larger and shallower than in Goura. The pectoral process 

 is thmner, but relatively rather more produced, in Didunculus. The humerus in (Edi- 

 cnemus, Otis, and Charadrius has a more longitudinally extended, thmner, and more 

 produced pectoral ridge than in Didus and the Columhidce ; there is a more marked 

 ectocondyloid tuberosity, which in Charadrius becomes a pointed process. 



There is nothing to be gamed by giving the details of the more striking differences 



' Traus. Zool. Soc. vol. iv. pi. 24. fig. 4. 



