PROFESSOR OWEN ON THE GENUS DINORNIS. 125 
defined by a slight elevation of the anterior, smoother upper intertemporal surface of 
the cranium, simulating a second upper transverse ridge (7) as before described. 
The postfrontal or postorbital processes (PJ. X. figs. 1-4, 12) are as broad as in 
D. robustus, consequently are relatively broader in proportion to the orbits and skull in 
D. elephantopus than in D. robustus: they are bent in their descent less obliquely back- 
ward. Upon the under surface of the roof of the orbits there is a well-marked oval 
depression, 3 lines in long diameter, posteriorly (ib. fig. 4,7), and a number of smaller 
more irregular depressions and foramina anterior thereto. 
The presphenoid (ib. fig. 4, 9) is compressed and is angular at the interorbital extent 
of its under surface, instead of being convex as in Dinornis robustus. ‘The depression 
above the base of the presphenoid and below the optic foramen is narrower than in 
D. robustus. The posterior part of the “ girdle” is not transverse to the axis of the 
skull but is inclined from the mid line outward and forward; and the presphenoid is 
deeper as well as narrower below the “ girdle.” 
The prefrontals (ib. figs. 1 & 4,14), anterior to the orbitosphenoids (ib. 10), and con- 
tinuous therewith, diverge from their basal confluence with the presphenoid (ib. 9), 
upward and outward; the part of their primitive blastema, interposed between the 
olfactory capsules, retains its unossified state at the hinder part of those cavities, save 
to the extent of one or two lines at the upper part, where a thin septal crest projects to 
the same extent from the expanded layer of the prefrontal, coalesced with the anterior 
wall of the cranium formed by the frontals and nasals. The posterior wall of the rhinal 
cavity is perforated by numerous olfactory nerve-filaments so as to form a “ cribriform 
plate”'. At the fore part of the orbit the outer plate of the prefrontal bends downward, 
outward, and forward toward the lacrymal (Pl. X. figs. 1 & 5,73), with which it forms 
the anterior wall of the orbit, chiefly convex thereto; the inferior border of this antor- 
bital wall is continuous with the semicircular frame or “ girdle” of bone* supporting a 
thin subreticulate ossified part of the olfactory capsule, forming a concavity looking or 
opening forward, and leaving a passage to the interorbital part of the olfactory cavity 
between its convex surface and the median part of the prefrontal. This median part, 
answering to the “lamina perpendicularis ethmoidei” of anthropotomy, the partial ossi- 
fication of which at the upper and back part of the olfactory chamber has already been 
noticed, has undergone the ossifying process about half an inch in advance of the cribri- 
form plate, for about an inch and a half along the base, which expands upon the fore 
part of the presphenoid; contracting as it rises to form the thin bony septum, it 
expands superiorly, especially at the hinder part, forming the platform supporting the 
nasals (ib. fig. 5, 15), and decreases vertically as it extends forward. ‘The “ girdle” divides 
the part of the olfactory cavity, partially partitioned by the bony septum, from the 
hinder expansion, where that septum is wanting. The undivided olfactory cavity 
1 «This ecribriform plate is a peculiarity in which Dinornis participates with Apteryw.”—Trans. Zool. Soc. 
vol. v. p. 350. 2 « Cingulum olfactorium,” ib. p. 349, pl. 56. fig. 1, 7. 
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