Cu. I.] OF THE DODO. 83 
The triangular surface for the attachment of the IZ. Levator ossis quadrati, occupies the digital fossa, 
extending round the posterior border of the foramen opticum ; it is prolonged outwards over the tympanic 
convexity, surrounded by a smooth depressed marginal tract of the latter, corresponding to a vascular 
circle. The irregular tympanic excavation is bounded above by the mastoid, and behind by the parocci- 
pital process. The post-temporal process of the mastoid is formed by a thick quadrantal plate projecting 
outwards with an inclination forwards, behind the temporal fossa; its outer edge is rough, and gives 
attachment to the external mandibular ligament, and viewed laterally projects downwards and forwards like 
a styloid process in front of the articular cavity for the anterior superior condyle of the tympanic. This 
cavity impresses the base and posterior surface of the post-temporal plate, thinning it internally ; its antero- 
posterior and transverse diameters, are three lines and a half. The mastoid process is a longitudinally 
extended, low, obtuse and thick pyramidal plate, projecting downwards so as to conceal the large quadrate 
superior pneumatic foramen, internal to it and between the tympanic articular cavities; its external smooth 
facet is separated by a shght ridge from the small posterior one, which is grooved at its base, and separated 
by a notch from the paroccipital process ; its inner surface is reticulate, and forms with the external a sharp 
edge. he inferior articular facet for the reception of the postero-superior condyle of the tympanic is 
oblong, three lines and two thirds long and two lines and two thirds deep, and composed of a smaller inner 
and a larger posterior segment, at right angles to each other ; beneath its anterior extremity is the external 
lacerated wall of a canal which ascends from the foramen lacerum posterius, curving forwards round the 
tympanic tube ; it passes into a groove, arching backwards to the lower angle of the upper pneumatic orifice, 
and terminating in a narrow canal which traverses the diploé at the floor of that orifice, emerges at the 
canalicular convexity on the occipital aspect. The paroccipital process presents a shallow groove at its 
base anteriorly, which widens as it ascends ; its floor is cellular above, behind the inferior tympanic facet ; 
_ below it curves inwards, and passes into a rounded orifice which perforates the outer wall of the canal 
just mentioned ; the groove lodges the smmus of the membrana tympani, which transmits its blood to the 
internal jugular vein ; its outer edge is undefined, the inner is sharp and gives attachment to the membrana 
tympani. 
Internal to it is a shorter but deeper concavity, also exposing pneumatic cells beneath the inferior 
tympanic facet. In the mouth of the tympanic tube is seen posteriorly the vertically oval orifice of a 
short canal, leading inwards and slightly forwards to the foramina ovale and rotundum of the vestibule, 
which are separated by an oblique grooved bar ; in front of it, is a large pneumatic orifice transmitting air 
to the diploé surrounding the labyrinth, and the oval orifice of the depressed basilar efferent pneumatic 
canal, passing forwards and inwards separated by a thin septum from the wide Eustachian tube: the 
efferent apertures from which open into the cells of the basilar protuberance, over which it passes con- 
verging to its fellow; the common orifice has already been described. The anterior wall of the tympanic 
tube is perforated by an aperture leading into the pneumatic canal. From the supra-orbital to the mastoid 
notch is two inches four lines and a half; between the opposite surfaces of the prefrontal, and of the 
paroccipital process inferiorly, is an interval of two inches; the anterior margin of the orbit is one inch six 
lines and a half deep, and from the temporal notch to the lower angle of the paroccipital, one inch five lines 
and a half. 
The broad superior facet of the cranium, on the removal of the beak so as to expose the upper surface 
of the turbinated ale of the ethmoid, presents a subhexagonal figure; the anterior border, corresponding 
to a line drawn between the anterior angles of the prefrontals, bemg only one half of the width of the 
posterior ; and the antero-lateral margins about twice as long as the postero-lateral: behind the line of the 
Z 
