PROFESSOR OWEN ON THE GENUS DINORNIS. 345 
axis is directed backward and a little downward. The occipital foramen (Pl. LVI. 
fig. 2, m) is shield-shaped, expanding to its upper border, which is overhung by the lower 
transverse superoccipital ridge (ib. 2, 2); the sides also slope toward the margin of the 
foramen: it is broader than in PI. LIII. fig. 3, but this I believe to exemplify range of 
individual variety. The basioccipital descends with a strong curve to its bimammillate 
(1') inferior line of union with the basisphenoid (ib. fig. 1, 1’,5): in the hollow of this 
curve, at the base of the peduncle, are the two rather unequal venous pits, perforated 
by small foramina of diploic venules. The precondyloid foramina (p) are two in number, 
on each side of the base of the condyle; they are very small. About one or two lines 
external to these is the large vagal foramen (v), perforating the bone, from within, 
obliquely downward and outward, and giving passage (in Apteryx) to the spinal acces- 
sory as well as the respiratory (eighth) nerve. Three lines external and in advance 
of the ‘vagal’ is the fossa, perforated anteriorly and inferiorly by the carotid (e), 
and posteriorly by the sympathetic and glossopharyngeal nerves and by a tympanic 
vein (s). 
The superoccipital, as in Pl. LIII. fig. 3, is of unusual breadth, and slopes from the 
lower transverse ridge (2,2) obliquely upward and forward. From the medial vertical 
ridge (3) to the paroccipital ridges (4') it is concave: the paroccipital ridge extends 
from the outer angle of the upper transverse ridge, downward and inward, to the pneu- 
mogastric fossa. The ridge is bent backward (ib. fig. 1, 4), and the upper half of the 
hinder part is thick and rough. The position of the paroccipital diapophysis in the 
Dinornis departs less from that in Crocodiles and Dicynodonts than in any other bird. 
On the superoccipital surface a venous groove extends, as in the first-described skull, 
from near the superoccipital tuberosity downward and outward, and terminates in a 
foramen penetrating the diploé. The lower superoccipital ridge formed by the exoc- 
cipitals (ib. 2) is more bent than the upper one, and its projection is chiefly due to, or 
shown by, the excavation of the surface of the bone beneath it ; the part extending to 
the upper border of the foramen magnum is nearly horizontal, overhanging that 
foramen like a pent-house ; the ridge laterally subsides about an inch from the paroc- 
cipital. Such configuration of the occipital surface (Pl. LVI. fig. 2) is rare in the class 
of Birds. 
The basisphenoid (ib. fig. 1, 5) is square-shaped; its hinder angles swell into the 
mamillar tuberosities (ib. 1'), which it conjointly forms with the basioccipital, and 
its anterior ones develope the pterapophyses (ib. 5’): these are about half an inch in 
length, directed outward, slightly forward and downward, with obliquely truncate ends, 
presenting a flat, roughish surface upward and outward to abut against the pterygoids. 
The sides of the basisphenoid are grooved by the Eustachian canals (e), which extend 
from the lower part of the tympanic cavity about a line in advance of the carotid fossa 
(c) forward and inward, gradually subsiding or becoming shallow to near the anterior 
border of the square basisphenoid platform (fig. 1,5): the breadth of the Eustachian 
VOL. V.—PART V. 22 
