PROFESSOR OWEN ON THE GENUS DINORNIS, 129 
linch 6 lines. The rostral part of the bone contracts behind, rather gradually, to form 
that septum (ib. fig. 1, s), which is much narrower, or less produced backward, than in 
Dinornis elephantopus. The mid tract of the rostral part (ib. fig. 2, 22), defined by the 
pair of grooves, is broader and flatter than in Dinornis elephantopus. The sides slope 
from the grooves less vertically to the alveolar margin; and the end of the beak is more 
obtusely rounded: it is broader, flatter, and shorter than in Dinornis elephantopus. The 
palatal surface of the premaxillary (ib. fig. 3,22) presents a gentle concavity, without 
median ridge or groove ; and the bony roof of that part of the mouth is continued entire 
further back in relation to the prenarial septum. 
The palatal part of the maxillary (ib. 21’) is gently convex from side to side, and sends 
back a short three-sided process for the articulation or attachment of the fore end of 
the palatine (ib. 20). 
Two of the skulls of Dinornis crassus, from the morass at Ruamoa, in the Walter- 
Mantellian series, had fortunately been packed up with the fine dark mud dried and 
hardened about them. On carefully picking this matrix away from the palatal surface 
I exposed a pair of long, rather narrow, and slightly bent plates of bone (ib. fig. 3, 13), 
with their concave side applied to the presphenoidal rostrum (ib. 9), which they under- 
lapped by their anterior third part, where their median edges come into contact. On 
being freed from the matrix, these lamine fell apart: and I do not think that any con- 
fluence here of the pair of plates was ruptured in their exposure; but the delicacy and 
extreme fragility of the plates may leave this an open question at present. I doubt 
whether the entire length of either plate is shown, as, in the skull presenting them, the 
upper mandible and the fore part of the presphenoidal rostrum has been broken off. 
Of that on the right side a length of 1 inch 9 lines is preserved, of the left lamina 
1 inch 6 lines. Both begin, behind, by an obtuse narrow end, and, converging, quickly 
expand to a breadth of 4 lines, which is retained for the course of an inch, when the 
lamella gradually narrows, and at their anterior divergence more quickly, to a point. 
The inner concavity and the outer convexity, which are moderate, rule in the transverse 
direction of the plate. Lengthwise the plate posteriorly is slightly concave, and then 
more slightly convex, where the plates converge anteriorly. The lower margin is 
straight, the upper and outer one convex in the degree of the expansion of the plate. 
These lamellae (Pl. XI. fig. 3,13) are homologous with the pair, confluent anteriorly, 
and underlapping the rostrum in the Emu (Dyomaius ater), determined (in my Second 
Memoir on Dinornis, 1846) as the vomer, and figured, with its symbolic number (13) in 
pl. 39. fig. 2 of that Memoir’. 
On the right side of the palate in the skull of Dinornis crassus with the divided 
vomer I found a more sinuously bent plate of bone in contact at its fore and inner 
surface with the hind end of the vomerine plate, extending some way forward parallel 
therewith, and continued backward, beyond the vomer, diverging, with gain of thick- 
1 Trans. Zool, Soc. vol. iii. 
