border of the optic foramen j at its deepest part it presents the foramen ovale. The oculo-motor aperture
opens within the posterior border of the optic foramen, beneath the orifice for the trochlearis nerve. The
form of the cerebral fossaj indicates that the cerebral lobes were broad and rounded in front, and elevated
above the level of the cerebellum; the mesial ridge dividing them is low and obtuse, aud subsides anteriorly
towards the inter-olfactory septum, which is slightly carinate vertically; the outer edge of the olfactory
foramen is subacute. The broad platform, formed by the interorbital septum between the olfactory and
optic outlets, is convex in both diameters; its posterior, thick aud rounded border projects over the groove
lodging the optic chiasma. The surface of the cerebral fossa is smooth, aud presents no trace of division
into compartments.
The strong, much compressed aud elongated upper mandille, corresponding to the two anterior thirds
of the cranium, may be regarded as forming a three-sided pyramid; whose base is bevelled off in a
direction downwards and forwards; the feebly uncinated apex projects beneath the level of the narrow
palatine facet; and a plane replaces posteriorly the edge to which the broad lateral surfaces incline above.
The thin upper margin of the base forms the hinge for the movements of the mandibular apparatus; from
its anterior and inferior angles pass backwards the palatine bones to meet on the sphenoidal rostrum, while
the slender pterygoids form a counter arch, springing from the inner angle of the inferior articular surface
of the tympanic on either side; its crown abuts against that of the palatine. The strong sigmoid zygoma
ascends from the external and inferior angle of the tympanic, to the centre of the outer edge of the base.
The length of the upper mandible, measured from the cranio-facial fine, is five inches eight lines, from the
same hue obliquely to the apex, five inches nine lines and a half; its greatest breadth is one inch seven
lines; and its height, opposite the inferior angle, is one inch five lines and a half.
The high, compressed core occupies the apical third; it is formed by the premaxillary, whose strong
mesial process, with the ento-nasal plate on each side, constitutes the upper beam of the mandible, a faint
linear impression indicating their respective boundaries; the narrow lanceolate nasal fissure, perforating
the basal two-thirds, divides the upper from the compressed lateral stems. The sutures between their
elements are wholly obliterated; judging from analogy, the lateral process of the premaxillary bifurcates
at a short distance behind the core, the inferior slip extending along the palatine surface, while the upper
sinks into the outer aspect of the maxilla, and is wedged posteriorly between it and the expanded foot of
the ecto-nasal limb, whose inferior boundary would probably be indicated by a line about an inch in
length, drawn from the malar process to the lower border of the nasal fissure; along the posterior half of
this line it meets the maxilla, which then passes internally to near the core, and forms the upper and lower,
thick and rounded borders of the lateral beam, except for a short space anteriorly.
The lateral stem thus constituted has an elongated subtriangular form, with the truncated apex
towards the core; the upper subconcave margin is three inches nine lines long; the base of two inches
and three lines, ascends obliquely backwards, forming an angle of 125° with the palatine edge, which is of
equal length. Viewed from above, the mandible presents a broad shallow excavation, impressing the outer
surface of the lateral beam on each side, and extending from its prominent external basal edge, behind
which the mandible is flatly compressed, forwards to the core.
This peculiarity in the skull of the Dodo, is due to the close approximation of the lateral stems
in their anterior half; the mandible being most constricted about an inch behind the core, where its
breadth is only seven lines, and its height one inch and three lines. The least breadth of each stem at
the same place is three lines and one-third, and from this point they become rather broader as they proceed
forwards, their lateral surfaces curving outwards to pass into those of the core; posteriorly they diverge
and receive the broad termination of the mesial beam between their elongated upper angles. Their
thickness also rapidly increases; that of the base is eight lines at the origin of the zygomatic process, but
diminishes towards the angles, especially the superior. Viewed in front, the base of the core conceals the
anterior portion of the floor of these fossa;, while behind, the posterior part appears shelving outwards;
the upper angle is also seen to curve obliquely backwards and inwards, grooving the upper border of the
stem. On tracing the groove downwards, it is seen to be continuous with a distinct broad impression,
occupying the deepest part of the fossa, separated posteriorly from a narrow tract of the general excavation
by a faint ridge, which curves downwards and forwards, becoming more distinct below; its concavity looks
upwards and forwards, and its anterior angle corresponds to the most constricted part of the mandible.
The anterior boundary is less distinct, it is formed by an oblique line descending forwards, in front of
which the lateral stem increases in breadth. The chord of these fossa;, corresponding to a line drawn from
the root of the zygoma to the greatest convexity of the core, is two inches and a half, and their greatest
depth four lines and a half.
The lateral stems in front are nearly parallel and separated only by a narrow clunk; at their base they
slightly diverge, and the upper angles also are, as it were, twisted outward.
The base bounds in front the irregularly triangular lachrymal fissure; immediately below the centre of
the external border is the origin of the zygoma, which passes backwards and downwards at an angle of
125° with the base: the lower half of the inner border is prolonged into a narrow, semi-lunar, antral plate,
five lines in depth, its inner surface slopes obliquely outwards and is vertically convex; the outer is
concave, a groove occupying its upper portion, at the, superior angle of which is a large pneumatic aperture
conveying air from the subocular sinus, and below it, several smaller ones; an elongated lacerated fissure
opens into the cancelli of the expanded base beneath the root of the zygoma, along which its upper angle
extends outwards. The lachrymal groove notches the base above the root of the zygoma and upper angle
of the antral plate; it corresponds to that on the prefrontal behind. The pneumatic diploe terminates
abruptly live lines and a half above this notch, fitting into the anterior extremity of the groove between
the prefrontal and turbinated ala, while the projecting inner angle of the prefrontal is lodged in a slight
depression on the outer surface of the protuberance. The prolonged upper angle formed by the ecto-nasal
limb, is a thin elastic plate, five lines and a half long and about four lines broad, with a sharp external,
and a thick rough internal, margin; it ascends to a higher level than the mesial beam, decussating it in
the centre of its course; it expands slightly outwards above, and is separated by a narrow chink from the
ento-nasal plate.
The mesial beam is formed anteriorly by the nasal process of the premaxillary; at its origin its basal
area is subcircular; the rentrant angle between it and the lateral process on each side corresponds to an
oblique fissure, leading forwards and outwards to the orifice of the horizontal vascular canal perforating the
core; it tapers gradually backwards for the space of an inch, and then continues of nearly the same transverse
diameter to the cranio-facial line, but diminishes rapidly in thickness; behind, it is supported by the ento-nasal
plates which pass beneath it and meet each other in the mesial hue inferior!/; an elongated narrow triangular
portion appears externally on either side of the nasal process, and causes the mesial beam to increase rapidly
iu breadth in its posterior half. The length of the mesial beam is three inches nine lines; its least breadth
towards its centre, where it is formed by the premaxillary nasal process is live lines and a half, its breadth at
the fronto-facial line is one inch; and its transverse diameter, before expanding into the core, nine lines.
The upper surface is flat behind with thick rounded borders; in front it declines gently outwards on each
side from a faint mesial ridge, and the edge, descending as it advances, disappears from the expansion of the
nasal process; the profile line has the same level for an inch posteriorly, and descends very gradually to the
2 B
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