21' transverse diameter of the internal, and by the greater breadth of the external condyle
which is flat, or slightly convex, and subcircular. In the Vulturidrc and Cathartes, the latter
is narrow and sigmoidal; convex in front, concave behind longitudinally, and rounded transversely.
In Cathartes the inner condyle is grooved at the base externally; and the trochlear
ridge is more oblique than in ordinary Pigeons. In the Dodo, its form is similar to that in
the typical genera of the Columbida?, and differs from that in the large Vultures, with which,
from a correspondence in absolute size, it may be more readily compared.
The absence of the posterior superior condyle in the typical Rasorcs, and its presence in
Pterocles, approximates, so far, this aberrant genus to the Columbida?.
VIII. The subtriangular body of the prefrontal is dove-tailed between the nasal bone and
antorbital process of the frontal, which advances along its outer edge to the lacrymal groove;
in the adult it is anchylosed to these bones above, and internally to the highly developed ala?
of the ethmoid; the prefronto-ethmoidal fissure being in most Pigeons wholly obliterated.
In Goura, a slender style separates its inner margin from the nasal, so that it is inserted by
gomphosis, into a deep semi-elliptical notch on the broad antorbital process. It is not subject
to removal by maceration, or such forces as would almost inevitably break off the upper
mandible ; and its occurrence in the fractured cranium of the Solitaire, may be regarded as
presumptive evidence of the Columbine ailinities of that extinct form.
In Pterocles, the prefrontal is anchylosed, but I have not been able to ascertain its
relation to the antorbital process; from the narrowness of its frontal aspect, it is not probable
that this process extends along its outer margin. In the typical Rasorcs, the prefrontal is
free, and projects greatly outwards; its inferior process is reduced to a slender curved style;
and the ala? of the ethmoid arc wanting, whde in Pterocles they are greatly developed, and
the prefronto-ethmoidal fissure is obliterated. The prefrontal is unanchylosed, even in the
adult, in all raptorial buds, except the aberrant genus Cathartes; the free external angle
supports the os superciliare; the prefronto-ethmoidal fissure is large and persistent; and the
antorbital process forms only a slight angular separation, between the shallow notch lodging
the apex of the prefrontal, and the deeply concave superciliary margin, which sweeps
rapidly outwards and downwards to the post-orbital process.
In Cathartes, the prefrontal is firmly united to the cranium; the supra-orbital membrane
is completely ossified, and gives increased breadth to the forehead. The olfactory
foramen opens into the apex of the infundibular turbinated ala of the ethmoid; the inferior
ala is anchylosed to the prefrontal below, but the prefronto-ethmoidal fissure remains.
IX. The size of the crotophytc impression, although variable in different species, according
to the resistance to be overcome, is very minute when compared with that in the Vulturida?,
or even Cathartes; in the Dodo it is exceedingly small, and is not compensated by an
increase in the area of the internal temporal surface.
X. The great extent of the digastric impression in Pigeons and in the Dodo, is well
contrasted with its small size in raptorial birds. The Rasorcs in this respect, as might be
anticipated, resemble the Columbida?.
X I. The presence of a single mesial supra-occipital aperture above the foramen magnum,
for the transmission of a vein, which arises from the muscles of the neck, and joins the posterior
cerebellar sinus. Among the Raptorcs, it occurs in some Owls, but I have not seen it in any
other family of birds. Its co-existence in the Dodo with other indications of affinity to the
Columbida?, shows the value of apparently trivial characters in determining the position of
an anomalous form.
XII. The general pneumaticitg of the cranial vault is greater in Pigeons, and the prefrontals
and sphenoidal rostrum are usually much more expanded than in the Vulturida? and Cathartes.
In these respects the Dodo resembles the Columbida?, and differs remarkably in the bullose
appearance of the prefrontal, and in the breadth of the rostrum, from the typical raptorial
birds. The Pterocles also approaches the Columbida? in these characters.
XIII. In the lower jaw, the curvature of the rami; their union at a more or less angular,
short and ascending, symphysis; the separation of the dentary, and, in some cases to a late
period, of the opercular elements; the presence of the interangular foramen in certain genera;
the large triangular digastric, or basal, facet; the small area of the temporal and pterygoid
impressions; and the differences in the form of the articular surface, corresponding to those
already alluded to, in the inferior surface of the tympanic, distinguish the lower mandible, in
the Columbida! from that in the Vulturida; and Cathartes: in the latter, however, the lower
jaw is more curved than in the less aberrant Raptores. We shall afterwards see how these
important differences are repeated in the Dodo. The development of the basal angles of the
digastric facet into the posterior and internal angular processes, so characteristic of the
typical Rasorcs, is observed in Pterocles.
The family characters of the skull in the Columbida;, just enumerated, are derived from
the consideration of parts, important cither in a physiological, or morphological, point of
view. One or more of them may be absent in aberrant members, or be common to different
types; but the whole, or a majority of them, occurring in the skull of an extinct form, would
justify us in assigning to it a place among this interesting and extensive group.
Before proceeding to a more minute description of the skull of the Dodo, and to a comparison
of it with that of other Pigeons, we may recapitulate shortly, those important differences
which warrant us in restricting such comparisons to the members of the Columbine group.
The skull of the Dodo differs from that of the Vulturida;, in the relatively small and
feebly uncinated core; in the elongation of the external nasal orifice, and absence of the
ossified scale; in the great relative size of the maxillary bone; in the obliquity of the
zygoma ; in the form of the mandibular surface of the tympanic; in the form of the palatine
bone; in the absence of the ossified septum narium; in the absence of the vomer; in the
form, and minute configuration, of the lower jaw ; in the anchylosis of the prefrontal, and
obliteration of the prefronto-ethmoidal fissure; in the greater breadth of the mtcrorbital
region, and absence of the os superciliare; in the small area of the crotophyte impressions,
and the great relative size of the digastric surface; in the existence of the mesial supra-
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