696 PROF. OWEN ON THE STERNUM OF NOTORNIS. [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 Binornis, as in Apterijx, the 

 breast-bone has shrunk in length rather than in breadth, and the 

 postmarginal notches, /, 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 Binornis. 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 in either. The non-articular portion of the anterior border of the 

 sternum is relatively greater in Aptornis than in Notornis (fig. I, e) ; 

 in this respect the larger extinct Coot more resembles both Apteryx 

 and Binornis. In Struthio and Bromaius the coracoid cavities, b, 

 almost meet upon the fore border of the sternum. In Casuaritis the 

 tripartite character of that border is the same, as regards the relative 

 lateral extent of the articular (6) and non-articular (c) 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, c ; and it may be remarked that the 

 respiratory movements pressing thereon precede the muscular actions 

 of flight. In the GalHnce the keel, which forms the chief part of 

 the breast-bone, is ossified from a separate centre, and the pair of 

 slender bifurcate 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 l)irds, 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 Porphyria to Tribonyx, thence to 

 Notornis, Ajitornis, Stringops, Apteryx, Biiiornis. But the modi- 

 fications are ada))tive, 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 



^ See the admirable works on the Birds of New Zealand, by Walter L. 

 Bullor, O.M.G., Sc.D., F.R.S. ; especially his ' Manual ' on the subject, 8vo. 



1882. 



