190 SHOULDER-GIRDLE AND BREAST-BONE. 



also twice as long as the coracoid ; the prsecoracoid forms a very slight projection ; and if there 

 was a minute clavicle in the recent state, it has been lost. The glenoid cavity is scarcely trace- 

 able, so that the fore-limb may have been absent. The Sternum is extremely interesting ; its 

 anterior margin is very transverse ; and has on it two very irregular and shallow coracoid grooves, 

 which are some distance apart. The costal processes are short. The first condyle for the 

 first large sternal rib is large, the others are smaller; the costal region is of small extent. 

 Behind the last condyle the external xiphoid begins at once to diverge ; this divergence is very 

 great ; the two bars are very narrow and arcuate, being bent inwards behind, and the notches 

 separating them from the middle part are very large and rounded above. The middle xiphoid 

 reaches to a less distance backwards than the outer bars, and it has a large, rounded, primordial 

 notch ; there is no appearance of an intermediate bar. The well-preserved moiety of the 

 Sternum of a young specimen is hatchet-shaped. The almost straight external xiphoid (its 

 curved cartilaginous end is lost) forms the handle of the ento-sternal part the blade. The 

 decay of the cartilage has left a deep notch, tending to separate the costal process from the 

 rest, so that it is very probable that there was a distinct centre to that part, as in our next 

 example the Rhea. If this were the case, then the Sternum of Dinornis robustus agreed with 

 Strut/do in the free external xiphoids; with Dromteus in the oblique, irregular coracoid grooves ; 

 and with Rhea in the number of ossifications. 



In Plate XVII, fig. 7, 1 have shown the Shoulder- and Breast-bones of the Rhea (R. americana 

 crossed with R. macrorhyncha), at the time of hatching, and magnified one and a half diameter. The 

 sharp-pointed scapula (sc.) is bent backwards above its base ; yet the curve of the whole bar is 

 but small. There is a triangular supra-scapular part (s. sc.), not ossified; an arcuate epicoracoid 

 base (e. cr.), very little developed into angles ; and between the scapula and coracoid (cr.) there 

 is a tract of cartilage a line in breadth : this is scooped to form the glenoid cup (gl.) behind, 

 and is formed into a small prae-coracoid hook (p. cr.) in front. The coracoid shaft is not pierced 

 below the hook, but an aponeurotic tract finished the " coracoid foramen." This is completed 

 in adult age by the spread of the periosteal growths ; and at that time the coracoid has become 

 relatively larger. Only the scapular and coracoid shaft-bones exist, and there is no clavicle ; so 

 that the Rhea agrees with the African Ostrich, the Apteryx, and probably also with Dinornis, 

 in this respect. The general shape of theRhea's Sternum is wedge-shaped ; the coracoid margin, 

 with its shallow, distant grooves (cr. g.) is very transverse ; this region is terminated at its angles 

 by the ear-like costal processes (c. p.). A wide shallow notch exists between the coracoid grooves, 

 which bear no greater relation to the whole margin than in Dinornis robustus ; behind the costal 

 processes the margin swells out to form three costal condyles (c. c.) ; then the Sternum narrows 

 gradually, and swells out gently in a somewhat spoon-shaped manner in the last third. There is 

 some distinction between the middle xiphoid and the outer, the former being pointed, as in an 

 acuminate leaf; but the lobulation is rather indefinite. The xjphoid region is very long 

 as compared with the praj-meso-sternum, but it is not ossified separately, for already a pair 

 of large ectosteal plates (" pleurostea ") occupy nearly half the cartilnge, and are only one 

 and a half line apart, mesially ; these plates have already nearly reached the posterior half 

 of the xiphoid region. But although these plates have nearly reached the coracoid grooves, yet 

 they do not finish the lateral prae-sternal regions (costal processes, c. p.), for here we find on each 

 side a new osseous centre the " pro-osteon ;" an osseous element encountered here for the first 

 time (except perhaps in Dinornis), but which will show itself, both symmetrical and azygous, in 



