122 PROFESSOR OWEN ON THE GENUS DINORNIS. 
between the fore and hind sides of the sternum. The corresponding part of the inner sur- 
face of the sternum of Aptornis otidiformis, or of Notornis (?) is not so defined, but is undu- 
lated by a rising, convex lengthwise, parallel with the mid third of the costal borders. 
The figures of the sternum of Aptornis defossor in Pl. XIV., being of the natural size, 
preclude the necessity of further admeasurements. 
There is no pneumatic perforation in any part of the sternum, which agrees, in this 
respect, with that provisionally referred to the smaller species of the genus. 
The generic distinction between Aptornis and the extinct gigantic Ralline bird called 
Cnemiornis is strongly expressed by the sternum. In Cnemiornis the ridged repre- 
sentative of the keel’ subsides much nearer the fore part of the bone; the costal border 
is relatively longer, and includes articular surfaces for seven sternal ribs; the body of 
the bone appears to retain its breadth for a greater extent as it recedes than in Aptornis 
defossor. The portions of sternum picked up with the other bones of Cnemiornis 
enable the above comparisons to be instituted, but they are not sufficient to give a 
satisfactory idea of the shape of the entire sternum in that genus. 
The pelvis of Aptornis defossor, figured of the natural size in Pl. XIV. fig. 1 and 
Pl. XV., exhibits a slight deformity or departure from the normal symmetrical figure at 
its fore part, which is somewhat bent to the right—the twist, which chiefly affects the 
neural spine and ilia, being most conspicuous when the bone is viewed from the front 
and from below, as in fig. 2. Pl. XV. It is doubtless an individual variety, and indicates 
the bird from which it was derived to have been aged. 
The articular surface of the centrum of the first sacral vertebra (Pl. XV. fig. 2, s 1) is 
transversely extended, measuring in that diameter 1 inch 44 lines, the vertical diameter 
at the middle being 5 lines; but this extends to 7 lines on each side beyond the neural 
canal, which is circular, and only 3} lines in diameter at its anterior outlet. The 
prezygapophyses (Pl. XIV. fig. 1,z) are large, with their outer borders bent strongly 
forward; the right is the largest, partaking of the asymmetry above noticed. The 
articular surface, concave transversely, is vertically plane, or rather convex. The fore 
part of the neural spine shows a rough surface for ligamentous attachment along the 
lower half of its extent; this surface expands to a breadth of 4 lines, then contracts to a 
point, beyond which the spine presents a sharp anterior margin to near the summit, 
where it again expands and coalesces with the contiguous parts of the iliac bones. A 
deep and narrow ilio-neural fissure extends backward on each side the spinal plate. 
The neurapophysis, developing the zygapophyses, is coextensive with the centrum, 
and expands beyond that element into a broad depressed diapophysis, confluent above 
with the ilium (Pl. XV. fig. 2,7): this process forms at its hinder angle a roundish flat 
surface (Pl. XIV. fig. 1, d) for the tubercle of the first free sacral rib. The articular 
surface for the head of that rib is large and flat on the left side (Pl. XIV. fig. 1, pl), 
but is small on the right side partaking of the asymmetry above noticed. The under 
' Trans, Zool. Soc. vol. y. pl. 63. fig. 9, s, 
