Cu. I.] OF THE DODO. 99 
The ratio in length of the upper mandible to the cranium, in various forms of Colwmbida, is seen 
by reference to Plate X.; in the ordinary Pigeon they are subequal, but in the stronger-billed fruit-eating 
genera, the beak is shorter than the cranium, and in Dedunculus, only half its length, while in the Dodo, it 
is twice as long. In the slender-billed species, the core is small, feebly hooked, and broadly rounded off 
apically ; it is relatively large, broad, and depressed in Geophaps; in Treron it is stronger and wedge-shaped ; 
but attains its maximum of development in Diduwnculus, where it is much compressed and more sharply 
uncinate than in the Dodo, assuming a pseudo-raptorial character, which, however, is negatived by the 
feeble osseous apex, and by the soft and foliated texture of the gnathotheca. The mesial beam is also 
much shortened in Didwnculus, but its great breadth gives the necessary strength to the resilient hinge, 
required for the movements of this powerful beak; it is covered by a vestige of the cere, which is much 
extended in certain Trerons, but arrives at its greatest extension in the Dodo. The peculiar characters 
of the maxilla and the obliquity of the zygoma in Pigeons, have already been described; in Didunculus, the 
horizontal portion of the maxilla almost disappears, but the very strong basal segment ascends obliquely 
to join the broad ecto-nasal limb, and from their junction the zygoma descends to gain the tympanic. The 
palatine tuberosity or plane in other Pigeons, is, in Didunculus, replaced by the greatly developed funicular 
tendon of the zxternal pterygoid muscle, which arises from a strong tubercle at the base of the under surface 
of the core; as it passes backwards external to the palatine bone, it is covered within by the membrane 
of the subocular sinus, and below by that of the palate, forming a surface on which the convexity of the 
lower jaw glides. The short lunate nasal fissure in Didwneulus, forms a striking contrast to its elongation 
in other Pigeons. 
The shape of the palatine bone in the typical Pigeons, is well seen in Treron, (Plate X, Fig. 3 ¢,) and 
the deviations from it, in that of the Dodo, are readily accounted for, by the shortening of the sphenoid and 
the contraction of the mandible; the chief differences consisting, in the absence of the inflected portion of 
the palatine process, which in Zreron diminishes the wide posterior nasal fissure; in the shortness of the 
sphenoidal plate, in relation to the abbreviated sphenoid; and in the less curvature of the nasal process, 
depending perhaps on the compression of the mandible. 
In the Didunculus, the palate bone is much elongatetl, beg attached anteriorly to the union between 
the very short lateral stem and the oblique ascending base of the maxilla, opposite the lower angle of the 
nasal fissure ; the middle segment corresponding to the nasal process is drawn out, forming the extended 
base of the lachrymal vacuity ; and from the great pneumaticity of the bone, the crest is expanded, narrowed, 
and subsides before reaching the sphenoidal plate. The nasal process is also but little apparent, the fossa 
between it and the crest being obliterated by the expansion of the diploé: the palatine process is a small 
curved triangular lamina, prolonging downwards the nasal concavity ; it subsides behind at the anterior and 
inferior angle of the sphenoidal plate, and in front towards the termination of the crest ; the large pneumatic 
aperture perforates the lower part of the sphenoidal plate. The small area afforded by the palatine, for the 
origin of the powerful internal pterygoid, is amply compensated by the great development of the tendon of 
that muscle. 
The pterygoid bone is relatively longest in Didwnculus, but has nearly the same form as in the Dodo, 
being destitute of pneumaticity, and of the sphenoidal articular surface ; in Geophaps it has a similar shape, 
but articulates, as in most other Pigeons, with the sphenoid; it is much inflated in Gowra &c., the pneu- 
matic aperture being at the posterior extremity. The form of the inferior articular surface of the tympanic 
varies in the different genera of Pigeons; this surface in the Dodo closely resembles that in Zreron and 
Calenas; in Geophaps, the articular surface on the outer segment is much reduced in size, though that angle 
of the bone is much expanded, and chiefly backwards. In Diduneulus, we observe the greatest deviation 
2D 
