BIRDS. 189 



symmetrical, faintly fivc-lobed form, which projects backwards considerably. The outermost 

 convexities answer to the outer xiphoid forks (e. x.) of the Fowl ; the next to the intermediate 

 (i. x.), and the semi-oval mesial lobe to the middle xiphoid bar (m. x.). Mesiad of each costal 

 region an ectosteal centre has appeared the " pleurosteon " (pi. o.) ; it has spread to the front 

 margin, and into the xiphoid region ; and the two centres cover two thirds of the anterior part ; 

 they also have reached the upper surface : these two are all the bony centres that will appear. The 

 posterior margin continues soft for a long while, even in the adult, and the bony matter spreads 

 backwards in a lobate manner ; the whole bone, also, becomes relatively longer, and steeper in 

 its sides. 



In the Emeu (Dromeeus irroratus) these parts are very similar to what we see in the 

 Cassowary (see Plate XVII, fig. 4, which shows the lower view of the Sternum of an embryo one 

 week before hatching, magnified to one and a half diameter). The narrow, feeble Shoulder-girdle 

 moiety has a similar gentle curve, which becomes very little more pronounced, even in old age ; 

 the scapula (sc.) has, at this stage, a very short, rounded, soft supra-scapula (s. sc.) ; and below, 

 there is a broad mass of hyaline cartilage connecting the pith of the scapular shaft with that of 

 the coracoid (cr.) ; this mass is slightly hooked to form the rudiment of a pra-coracoid (p. cr.). 

 The coracoid is a small phalangiform ray, narrower than in the Mooruk, and not having a 

 foramen ; the epicoracoid base (e. cr.) is of small extent, it is soft at present, and of a semilunar 

 form. The clavicles (cl.) are twice as strong and large as in the Cassowary, and have the same 

 relations ; in the old Bird they have become elongated and arcuate, so that by a little more 

 development they would have formed a furcula very similar too, but feebler than, that of the 

 Tinamou. The Sternum is very similar to that of the Mooruk, but it is narrowest in front and 

 widest behind ; the costal processes (c. p.) are sharper, and the smaller coracoid grooves (cr. g.) 

 overlap the left below the rigid ; the rostrum is faintly foreshadowed between and below these 

 by a double pimple of cartilage. There is the same quinquelobate form of the huge xiphoid 

 plate; but this spreads much more, especially the anterior and outer lobes (e. x.). As the right 

 coracoid groove and lower lip is larger and further backwards than the left, so the right half of 

 the xiphoid region is further backwards, and the largest ; the primordial fissure (x. f.) is half an 

 inch long, and is seen to separate the wide five-lobed xiphoid mass un symmetrically. The Sternum 

 has middle anterior convexity, and a general sinuous convexity behind ; there are four pairs ot 

 costal condyles (c. c.), and a pair of .ectosteal " pleurostea," as in Casuarius. In an Emeu six weeks 

 old (D. novce-hollandice], I found these to have coalesced at the mid-line, and to be creeping in a 

 two-eared form down to the second third of the xiphoid region, which had become much more 

 convex, had lost much of its lobate outline, and to have acquired a very elegant acuminato- 

 ovate form, the middle region projecting in a pointed manner very far backwards. In the old 

 bird, there is still a large unossifiecl xiphoid margin ; but it is, relatively, much broader and 

 shorter ; the bone is much more pinched behind the costal condyles ; the costal processes have 

 become long and erect, and there is a shallow fossa below, along the mid-line of the general 

 shield-like convexity of the bone. 



The feeble coraco-scapular bar of Dinornis robustus, Ow., is well displayed in Professor 

 Owen's ninth paper on this genus (see ' Zool. Trans.,' 1866, pi. 55); and the Sternum of both 

 the old and young (the latter a moiety) is beautifully shown in the photographs of the York 

 specimens mentioned by me in my paper on the Struthious Skull (see 'Phil. Trans.' 1866, 

 p. 163). The whole of this gently curved bar is very narrow, the scapula being the narrowest, and 



