122 PEOFESSOE OWEN ON THE GENUS DINOENIS. 



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 (1) is not so defined, but is imdu- 

 lated by a rising, convex lengthwise, parallel with the mid third of the costal borders. 



The figures of the sternum ot Aptornis defossor in PI. 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 refeiTed to the smaller species of the genus. 



The generic distinction between Aptornis and the extinct gigantic Kalline 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 PI. XIV. fig. 1 and 

 PI. XV., exhibits a slight deformity or departure &om 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. PI. 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 (PI. XV. fig. 2, s i) is 

 transversely extended, measuring in that diameter 1 inch 4^ 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 3J lines in diameter at its anterior outlet. The 

 prezygapophyses (PI. XIV. fig. 1, z) are large, with their outer borders bent strongly 

 forward; the right is the largest, partaking of the asymmetiy 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 (PI. XV. fig. 2,i): this process forms at its hinder angle a roundish flat 

 surface (PI. XIV. fig. 1, d) for the tubercle of the first free sacral rib. The ai-ticular 

 surface for the head of that rib is large and flat on the left side (PI. XIV. fig. \,pl), 

 but is small on the right side partaking of the asymmetry above noticed. The under 



' Trans. Zool. Soo. vol. v. pi. 63. fig. 9, s. 



