PROFESSOR OWEN ON THE GENUS DINORNIS. 139 
than in them, is consequently relatively smaller, especially to the prosencephalic one ( p) 
in D. gigas. The foramen ovale is more oblong, and at the upper part of the side of 
the cavity. The prelacerate and optic foramina present the same size and position as 
in D. rheides, indicating, together with the size of the mesencephalon, relatively smaller 
eye-balls in D. gigas. The sella (s) is somewhat deeper, but not larger in other dimen- 
sions; it is perforated behind by the entocarotid canal. The prosencephalic wall has 
the same configuration (indicative of the longitudinal indent of the cerebral hemisphere) 
as in Dinornis rheides. The rhinencephalic fosse (r) are a pair divided by an obtuse lon- 
gitudinal ridge representing a “ crista galli” 24 lines thick; each fossa is elliptic, 5 lines 
by 4 lines in long and short diameters, with from eight to ten perforations, the largest 
leading from the outer side of the cavity. The cribriform plate is extremely thin’. 
Skull of Dinornis casuarinus, Ow. (Plate XIII. figs. 1-8.) 
The relations of locality affecting the sternum and limb-bones of D. rheides, and the 
sole cranium therewith collected and transmitted to Mr. Sumpter, without a trace of 
any determinant bone of Dinornis casuarinus, solved the doubt which had long troubled 
me in regard to the skull, which, in respect to general size, might seem to belong to 
either of two such nearly matched species. It was with lively satisfaction, therefore, 
that I saw in a series of bones belonging to one and the same skeleton of a Dinornis 
casuarinus from the famous Glenmark swamp, submitted for sale to the Geological 
Department of the British Museum, in the course of the present year, by William 
Reeves, Esq., that the skull presented, with a general correspondence of size in the 
cranial part (Pl. XIII. figs. 2, 3), unquestionable specific differences throughout from 
that of Dinornis rheides, and more especially in the forms and proportions of the man- 
dibular parts of both upper and lower jaws (ib. figs. 4-8). 
The occipital surface (ib. fig. 5) almost exactly repeats the dimensions of the same in 
Dinornis rheides, but with the following differences :— 
The basioccipital descends more abruptly and vertically, the vagal and carotico-sym- 
pathetic foramina are larger, the tuberosities (ib. fig. 3,1’) are less prominent or defined 
at the back part of the basioccipito-sphenoidal quadrate surface or “platform.” The 
upper border of the foramen magnum is much thicker, and is channelled, as if for a 
venous sinus. The superoccipital rises above the foramen, as a triangular tuberosity 
(ib. fig. 2), to the level of the calvarium. The superoccipital depressions, having this 
tuberosity intervening instead of a vertical crista, are wider apart. The ridges descending 
from above the foramen magnum, and diverging to the paroccipitals, are broader and 
"more pronounced ; they define, with the back part of the basioccipito-sphenoidal surface, 
a triangular area, from near the centre of which projects the occipital condyle. There 
' This plate being broken away at its middle led me into the error of supposing the olfactory nerve to have 
escaped, as in birds generally, by one large foramen, in the first description of the cranial cavity, Memoir Y. 
(Trans. Zool. Soc. vol. iv. p. 64). 
VOL. VII. PART . Jan. 1870. U 
