342 
so defined, but is undulated by a rising, convex lengthwise, parallel with the mid third 
ostal borders. 
of ier a s of the sternum of Aptornis defossor in Pl. LXXXIX., being of the natural 
size, preclude the necessity of further admeasurements. 7 
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. LX XXIX. fig. 1 
and Pl, LXXXVIII., exhibits a slight deformity or departure from the normal symme- 
trical 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. LXXXVIII. It is doubtless an indi- 
vidual 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. LXX XVIII. 
fig. 2,1) is transversely extended, measuring in that diameter 1 inch 42 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 34 lines in diameter at its anterior 
outlet. ‘The prezygapophyses (P1. LXX XIX. 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 transyersely, 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 toa 
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. LXXXVIIL. fig. 2,7): this process forms at its hinder angle a 
ToeRiaS flat surface (Pl. LXXXIX. fig. 1, d) for the tubercle of the first free sacral 
rib. The astiotilar surface for the head of that rib is large and flat on the left side 
(ib. fig. 1, pZ), but is small on the right side, partaking of the asymmetry above noticed. 
The under surface of the centrum is carinate; the keel beginning 2 lines behind the 
' Pl, LXVI, fig. 9,5, 

