PROFESSOR OWEN ON THE GENUS DINORNIS. 349 
prelacerate (f) foramina, beneath which there is thus a smooth depression (10) capable 
of receiving the end of a man’s thumb on each side and above the origin of the 
presphenoid. In advance of these depressions the outer plates of the neurapophyses 
(Pl. LVI. fig. 1, 14) extend obliquely outward as they rise, forming the sides of the 
larger rhinal chamber (PI. LIV. fig. 1, x), and passing uninterruptedly to coalesce 
with the superorbital expansions of the frontal (neural spine, Pl. LIII. fig. 1, 11). 
From the upper and anterior half of the presphenoid rostrum, the inner plates of 
the neurapophyses (11)—foremost terminal ones of the series—converge and coalesce 
into a vertical wall of bone (Pl. LVI. fig. 3,14’), thickest, lengthwise, at its middle 
part and thence gradually thinning off to both posterior and anterior margins, but 
thinnest vertically at its middle part, and expanding both below and above. Superiorly 
the expansion attains a breadth of 8 lines, with a flattened upper surface (ib. fig. 3, 14’ ) 
supporting the fore part of the nasals (15), which part is overlapped by the premax- 
illary, and with the under surface forming an arch on each side over the fore part of 
the rhinal chamber. 
The base of each of these neurapophysial plates, prior to their rising to converge 
and coalesce, developes a strong, thick, dense, and smooth girdle of bone around 
the orifice of communication between the rhinal chamber and the corresponding 
nasal passage: the girdle (ib. fig. 1, g, g', g’) is not entire; about one-sixth is incom- 
plete at its fore part; the orifice it otherwise would encompass is of a triangular 
form, with the angles rounded off (ib. 19). The hinder side or bar (g) is transverse 
to the skull’s axis, and is 1 inch long; the medial side (9') is in the skull’s axis, 
and is 10 lines long; the third side, partly formed by the bending of the outer 
end of the hind bar, extends obliquely forward and inward for 6 lines, leaving about 
the same extent of the circumference incomplete at its middle, between the above and 
the process (ib. g’), which extends transversely outward. The inner part of this thick 
border or girdle is defined from the base of the neurapophysis developing it by a narrow 
groove ; the hind part increases in depth as it extends outward and makes a bold bend 
forward and inward, with the convexity projecting into the fore part of the orbit, as 
it bends to form the anterior part of the girdle. ‘There is a small perforation at the 
convex bend, and the upward continuation of this part of the wall, which is concave 
forward, becomes as thin as fine paper, subreticulate, and continuous with the delicate 
bony support of a turbinal (ib. 19). We have here the commencement of the accessory 
or apophysial part of the neurapophysis, which becomes developed into the most con- 
spicuous part of the ‘ frontal antérieur’ of Cuvier, e.g. in Reptiles. But in Dinornis 
the ‘ prefrontals’ are unwontedly developed in their essential parts, and almost exclu- 
sively devoted to the olfactory chamber, which is serially homologous with the orbit 
and the tympanum, as the antecedent nasal passage conducting the air thereto is the 
homotype of the meatus auditorius externus in the hinder organ of special sense. 
On removing the centrum and lower portions of the neurapophyses of this region of 
