188 SHOULDER-GIRDLE AND BREAST-BONE. 



fills the egg-shell notable changes have taken place in the Shoulder-plate, although the Sternum 

 has increased principally in size and convexity, but without any ossific deposit. The scapula 

 (fig. 6, sc.) has acquired an ectosteal coating, leaving a somewhat curved supra-scapula (s. sc.) 

 still soft; the meso-scapular and glenoid (gl.) regions also are still unossified. The waist of 

 the hourglass-shaped coracoid (cr.) is invested with bone, leaving the head and the epicoracoid 

 regions (e. cr.) still soft. The large Chelonioid pra>coracoid (p. cr.) will receive its bony 

 matter direct from the scapular shaft, exactly as in the Chelonians ; the cleft (cr. n.) between the 

 two bars is extremely narrow below, but has expanded above. No morphological changes will 

 take place in this two-legged bar ; but, histologically, it will be modified by complete conversion 

 into bone, without adding any new centres. There is no clavicle in Struthio ; the large 

 anterior bar is the lump out of which morphological change (metamorphosis) might have modelled 

 the "meso-scapular" and " prse-coracoid segments." The Sternum (fig. 5) soon acquires its 

 permanent outline ; it is oblong, but pinched between the costal condyles (c. c.), an,d then quickly 

 expands to form the external xiphoids (e. x.), which are rather broad, arcuate, and pedate ; they 

 are separated from the middle xiphoid (m. x.) by a large, rounded notch; this process has its 

 own convexity, distinct from that of the main part of the ento-sternum ; it is tongue-shaped, and 

 projects further backwards than the outer bars. There are five condyles (c. c.) surmounted by 

 an angular costal process (c. p.) ; the coracoid grooves (cr. g.) are some distance apart, and are 

 separated by the rudiment of a notched rostrum. I have not seen more than two ectosteal 

 patches in the Sternum of Strulhio (Hunt. Mus., No. 1366) ; but I have at hand no specimen 

 near hatching time to settle this point ; for secondary or smaller centres soon coalesce with the 

 main pieces. The Sternum of Strut/do becomes completely ossified in old age, and a pair of 

 small inner notches appear behind, separating the intermediate xiphoids from the middle 

 process. The sternal ribs (s. r.) are still soft in the youngest Struthio; but ossification has 

 commenced in the vertebral ribs (v. r.). 



In the ripe chick of the Mooruk (Casuarius Bennettii, Plate XVII, fig. 3, magnified to one 

 and a half diameter, and from below), we see a very long, slender, sinuoso-arcuate scapula (sc.), 

 almost ossified, with a soft blunt-pointed supra-scapula (s. sc.) ; the swollen meso-scapular and 

 glenoid (gl.) base is also soft, as is also the beak-like, arrested prse-coracoid. The coracoid, 

 which is smaller than in Struthio, runs in the same curved line as the scapula, but makes no 

 angular bend; its substance is pierced to form the usual foramen, and its base (e. cr.), still soft, 

 is broadly pedate ; from the deficiency of the prse-coracoid bar the " notch " is widely open 

 below. 



The right clavicle is two and the left one and a half lines in length (fig. 3, cl.) ; they are 

 spindle-shaped, and are perched up on the mesial side of the prae-coracoid, this being the place 

 where the skin at the base of the neck is tucked in, expanding again over the thorax. These bones 

 form no morphological union with the endo-skeletal parts of the thorax ; but continue as inde- 

 pendent as in the Lizards. The Sternum is heart-shaped, and is tolerably convex all over its 

 lower surface; its costal processes (c. p.), and condyles (c. c.) project furthest outwards; the 

 former is not much larger than the latter, of which there are five. The coracoid grooves are 

 large and symmetrical ; the outer lip is a manifest " out-growth," and each terminates in a 

 rounded elevation ; between these there is a large primordial notch. The xiphoid region forms 

 two thirds of the Sternum ; it suddenly narrows behind the fifth costal condyle ; it then bulges, 

 and narrows again ; after this, there is an ear-like expansion, the cartilage then taking on a 



