194

170

surface (fig. 6, z'), and then rapidly diminishes in thickness, curving inward towards its
fellow, which it does not quite meet, above the neural canal (Pl. LXII. fig. 5, n). The
anterior end of the centrum of the atlas occupies the notch (c) between the hypapophysis
and neurapophysis, completes the occipital cup, and gives attachment to the ligament
answering to the 'odontoir in anthropotomy. The figures of the atlas in Pl. LXII..
are of natural size : the specimen was obtained with the incomplete skull from the
fissure at 'Timaru.'

5. Scapula-coracoid Arch of Dinornis robustus.

The existence of such arch in the skeleton of Dinornis was inferred, in the Memoir
on Palapteryx (p. 124), from the articular depressions in the sternum (Pl. XXXV.
fig. 2, c, c) ; and , by the peculiarly small size, shallowness, and shape of these depres-
sions, I recognized the convex extremity of the bone (Pl. LXIV. FIGS. 2, 3, 4, x), forming
part of the skeleton of the Dinornis robustus from Manuherikia, as being the sternal end
of the coracoid. It presents a rather irregular convexity, of an oval shape, 10 lines by
6 lines in the two diameters, with a rough surface indicative of ligamentous union with
the sternal fossa, not of articulation by a synovial joint , as in birds of flight. From
the tuberosity (x) the bone (52) rises straight, decreasing in thickness and increasing in
breadth at its upper end, which is confluent with a much longer and thinner bone (51),
forming with the coracoid a widely open angle, and slightly curved in its course. This
bone I take to be the 'scapula' confluent with the coracoid, partly from characters of
proportion and shape and partly from the analogy of the scapulo-coracoid arch in the
Apteryx 1. In this bird the coracoid and scapula are confluent, and present relative pro-
portions as to length like those in Dinornis. But the coracoid is relatively much broader
in the Apteryx ; its sternal end is adapted to a long groove, as in most other birds ; it
also shows a perforation near its scapula end, and a more important difference in the
presence of the glenoid cavity for the humerus on the posterior margin of the scapulo-
coracoid confluence. There is no trace of such articular cavity in the scapulo-coracoid
arch of Dinornis, but in place thereof a rough, slightly produced ridge (fig. 4, r), to
which, if any rudiment of humerus existed, it must have been suspended by ligament.
I, however, infer that such appendage of the scapular arch did not exist in the living
bird ; that the Dinornis offers the previously unknown and unique exception to the
tetrapodal type in Birds that the anterior members, like the posterior ones in Cetacea,
were represented only by their supporting arch, and that this arch was limbless, as it
is in Anguis among the Lacertian Reptiles.

The scapula (Pl. LXIV. figs. 2, 3, 4, 51) soon decreases in breadth, from 11 lines at
the confluent part (m) to 7 lines within an inch from that part, beyond which it more
gradually narrows to a breadth of 5 lines at the extremity ; the thickness of the bone
gradually decreases also from the coracoid confluence (fig. 4, m), viz. from 4 lines to

1. Ante, p. 34, pl. ix. fig. 4, e,f,g.