696 PROF. OWEN ON THE STERNUM OF NotroRNIS. [Nov. 28, 
of baked eggs in the stone ovens exposed beneath several feet of 
superficial soil, that the great wingless birds supplied the immigrant 
Polynesians with their staple animal diet, until that source was ex- 
hausted through such extirpation. 
Returning to my more usual field of work (the skeleton), I would 
remark that the sternally-reduced Rallines do not offer in the rest 
of their organization a much greater degree, if any, of difference from 
Struthio than Apteryx presents. In Dinornis, as in Apteryx, the 
breast-bone has shrunk in length rather than in breadth, and the 
postmarginal notches, f, with the corresponding processes, g, are 
retained. Rudiments of these notches and processes are visible in 
Struthio, with a relative breadth of the keelless breast-bone 
approaching that in Dinornis. In the less broad, longer, triangular 
shape of the sternum, devoid of both notches and processes, Rhea 
comes nearest to Aptornis, and there is no trace of a manubrial pro- 
cess ineither. The non-articular portion of the anterior border of the 
sternum is relatively greater in Apéornis than in Notornis (fig. 1, e) ; 
in this respect the larger extinct Coot more resembles both Apieryx 
and Dinornis. In Struthio and Dromaius the coracoid cavities, 6, 
almost meet upon the fore border of the sternum. In Casuarius the 
tripartite character of that border is the same, as regards the relative 
lateral extent of the articular (2) and non-articular (ec) portions, as 
in Notornis (fig. 1). 
In the young Coot the sternum is ossified from two transversely 
parallel centres. These first harden the primitive cartilaginous 
expanse near the costal borders, ¢; and it may be remarked that the 
respiratory movements pressing thereon precede the muscular actions 
of flight. In the Galline the keel, which forms the chief part of 
the breast-bone, is ossified from a separate centre, and the pair of 
slender bifureate bony tracts beyond the costal borders have each a 
centre of ossification, distinct from the parial centres, common to the 
class, from which the main sternal plate is ossified. But these five 
points of ossification are exceptional in the class of birds, and relate 
to adaptive peculiarities of form in a particular group. They have 
been viewed as the rule of avian sternal development, and the two 
pairs of centres in the Common Fowl have been homologized with 
the hyo- and hyposternals of Chelonia ; but this only shows how an 
embryology misconceived may mislead in the quest of homologies. 
The New-Zealand birds afford instructive examples of the pro- 
gressive loss of the volant faculty, with concomitant modifications of 
the parts of the skeleton giving origin to the pectoral muscles’. The 
keel progressively shrinks from Porphyrio to Tribonyx, thence to 
Notornis, Aptornis, Stringops, Apteryx, Dinornis. But the modi- 
fications are adaptive, and accompany a sum of organic characters 
truly indicative of natural affinity ; which sum, as it forbids the Kivi 
to be associated in the same order with the Wood-hen, or Stringops 
with either, equally removes Apteryx from Aptornis, and the latter 
1 See the admirable works on the Birds of New Zealand, by Walter L. 
oe O.M.G., Se.D., F.R.S.; especially his ‘Manual’ on the subject, 8vo, 
1882. 
