Cu. I.] OF THE DODO. 91 
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 fossie, 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 tracmg 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 fossee, 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 chink ; 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 lmes 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 fromthe subocular smus, and below it, several smaller ones; an elongated lacerated fissure 
opens into the eance//i 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 diploé terminates 
abruptly five lines and a half above this notch, fitting into the anterior extremity of the groove between 
the prefrontal and turbinated ala, while the projecting immer 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 Imes 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 shghtly 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 line inferiorly; an elongated narrow triangular 
portion appears externally on either side of the nasal process, and causes the mesial beam to increase rapidly 
in 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 five lines and a half, its breadth at 
the fronto-facial ime is one inch; and its transverse diameter, before expanding into the core, nine lines. 
The upper surface is flat behind with thick rounded borders ; im 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 
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