138 PROFESSOR OWEN ON THE GENUS DINORNIS. 
This is shown in the section of the cranium figured in Memoir V. (Trans. Zool. Soc. 
vol. iv.) pl. 24. fig. 4, also in the specimen with the outer table of the calvarium removed, 
in Memoir III. (op. cit. vol. iii.) pl. 53. fig. 6, and in the specimen with the outer table 
removed from the basis cranii, ib. fig. 5. The thickness of the cranial walls is 
strikingly shown at the lines of suture, or rather “harmonia,” of the cranial bones in 
the skull of a young individual of Dinornis giganteus, Memoir V. (op. cit. vol. iv.) pl. 24. 
fig. 3, 7, in which the extension of the compact table from the outer to the inner 
surface of the cranial bone is shown along the harmonial surface: such continuous 
plate becomes absorbed after the confluence of the cranial bones is completed; and the 
diploé then gives free and uninterrupted passage to the air through the thick walls of 
the skull. Consequently the inner table alone is moulded upon the brain, the most 
prominent upper parts of which (at the prosencephalon), though sometimes obliterating 
the diploé, as is partially the case in Dinornis rheides, rarely (as in that species) pushes 
the outer table above its level so as to indicate the whereabouts of the cerebral hemi- 
spheres. The breadth as well as length of the fronto-nasal roof of the skull (fig. 3, 11) 
anterior to the prosencephalic risings (if these happen to be marked) are characteristic 
features of Dinornis; and I may add that, among other distinctive characters noted in 
former Memoirs, Dinornis differs from the Struthionidew in the upper expansion of the 
coalesced prefrontals being covered by the nasals and not appearing at the upper sur- 
face of the skull, in the absence of an expanded outer plate of the lachrymal, and in the 
almost equality of breadth of the occiput with the postorbital part of the skull. 
Of the Cranial Cavity of Dinornis giganteus. (Plate XIII. fig. 9.) 
With some parts of the skeleton of a Dinornis giganteus presented to the British 
Museum by Mr. Luxmore, including most of the vertebrae and pelvis, was the cranium, 
with some other fragments of the skull, all much abraded or fractured. The locality of 
these remains is unknown. ‘The thick and coarse-celled diploé of the cranial walls was 
extensively exposed; and it seemed to me that the best use to make of the specimen 
was to expose in it by a vertical longitudinal section the extent, shape, and other 
characters of the cranial cavity in that species. 
These, therefore, I propose to compare with those detailed in the foregoing account 
of D. rheides. 
The length of the cranial cavity is 2 inches 8 lines, the breadth 2 inches 5 lines, the 
height 1 inch 4 lines, the measurements being taken at the same points as in the 
cranium of D. rheides. The cavity is unequally divided by the vertical tentorial ridge, 
the prosencephalon being longer in proportion to the cerebellum than in D. rheides or 
the species figured in pl. 24. fig. 4, Vol. IV. The tentorial ridge is interrupted, as in 
those species, by the passage of the longitudinal into the lateral or petrosal sinus. 
Beneath this the petrosal wall of the labyrinth makes a greater prominence than in the 
smaller Moas above cited. The mesencephalic fossa (Pl. XIII. fig. 9, m) is not larger 
