PROFESSOR OWEN ON THE GENUS DINORNIS. 345 



axis is directed backward and a little downward. The occipital foramen (PI. 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 PL 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'.s) : 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 Jpteryx) to the spinal acces- 

 sory as well as the respiratory (eighth) nerve. Three Unes 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 PI. 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 diploe. 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 (PI. 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. r), 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, &): the breadth of the Eustachian 



VOL. V. PART V. 2 z 



