356 PROFESSOR OWEN ON THE GENUS DINORNIS. 
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. LII. fig. 5,). The 
anterior end of the centrum of the atlas occupies the notch (¢) between the hypapophysis 
and neurapophysis, completes the occipital cup, and gives attachment to the ligament 
answering to the ‘odontoid’ in anthropotomy. The figures of the atlas in Pl. LIL. 
are of the natural size: the specimen was obtained with the incomplete skull from the 
fissure at ‘ Timaru.’ 
§ 5. Scapulo-coracoid Arch of Dinornis robustus. 
The existence of such arch in the skeleton of Dinornis was inferred, in my Second 
Memoir, from the articular depressions in the sternum’; and, by the peculiarly small 
size, shallowness, and shape of these depressions, I recognized the convex extremity 
of the bone (Pl. LV. 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*. In this bird the coracoid and 
scapula are confluent, and present relative proportions as to length like those in Dinornis. 
But the coracoid is relatively much broader in the Apteryz ; its sternal end is adapted to 
a long groove, as in most other birds ; it also shows a perforation near its scapular 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 archof Dinornis, but in place thereof a rough, 
slightly produced ridge (7), 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. LV. 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 Trans. Zool. Soe. vol. iii. p. 316, pl. 43. figs. 1-3. 
? Thid. vol. ii. p. 308, pl. 55. e, fg. 
oe a ee eae 
= 
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