228 MR. W. K. PARKER ON THE OSTEOLOGY 



may be compared to the upper episternal piece of a Pigeon, thinned away from below 

 upwards. The episternum exists as a rudiment in Apteryx, at the centre of the huge 

 fault in the anterior part of the sternum ; and it gives this retiring anterior margin, 

 between the widely separated coracoid grooves, an elegant bilunate shape. This episternal 

 deficiency appears in the " wingless " Rails, e. g. Brachypteryx ; it is also really present 

 in the Tinamou as a wide fossa, having a pneumatic hole at its base, below which 

 passage the anterior edge of the keel begins. The episternum of the Tinamou is but 

 the rudiment of that of the Fowl, which bird has it large and conspicuous, standing right 

 forward like the figure-head of a ship (PI. XLI. figs. 9 & 10). There is the same feeble-, 

 ness of expression in the " hyosternal " crests of the Tinamou (Pis. XXXIX. & XLI. 

 fig. 1, hs.) : in the Fowl (PI. XLI. figs. 9 & 10, hs.) they stand boldly forthright, like 

 the episternum ; but here they are almost upright, save that they bend outwards ; 

 they are also only about half the size of those of the Fowl : behind them is the groove 

 on each side for the three sternal ribs : the whole articular surface of the upper 

 (hyosternal) edge of the sternum is 4 lines in extent — one-sixteenth of the entire 

 length of the sternum. The Rhea has only three pairs of h8emapophyses articulating with 

 the sternum; and, among the higher " Grallse," the Tiger Bittern {Tigrosoma leucolo- 

 phum) has no more ; the Common Cassowary has an additional rudimentary pair in 

 front, the Apteryx and the Emu four perfect pairs, and the Great Ostrich {Struthio 

 camelus) five pairs. The hyosternal crests are nearly as well developed in the Apteryx 

 as in the Tinamou, and the hyposternals are marked off; they are very different from 

 those of the Tinamou, but not more simple ; in the latter (Pis. XXXIX. & XLI. fig. 1, 

 hys.) each bone is an elegantly bowed style, 4 inches long by a line in average breadth : 

 in the Apteryx each process is a flap of thin bone, 9 lines by 3, but bowed also in the 

 same style as in the Tinamou. The best figures fail to show the elegance of these pro- 

 cesses and the extreme beauty of the whole sternum in the latter bird ; beauty, however, 

 seems scarcely to have been aimed at in the construction of the Apteryx's breast-bone. 

 As in the Fowls, the middle bony piece of the Tinamou's sternum (the entosternum) is 

 principally composed of keel ; indeed the keel is merely broadened into a gently convexo- 

 concave side-plate on each side (PI. XLI. fig. 1 , es.), the margin of these up- and out-stand- 

 ing crests of bone is sharp, and the whole outline has the same elegant bend as the hypo- 

 sternum, the concavities of these outlines being opposed so as to leave a membranous in- 

 terspace nearly ten lines across at the middle. The body of the sternum thickens abruptly 

 at the end ; all is ossified ; and the xiphisternal termination (xs.) is truncate, and is 3 J lines 

 across. The hyposternals are well marked and tinamoid in the Great Ostrich (Struthio) ; 

 and there is a pluvialine notch on each side the xiphisternal end : all the sternum is 

 ossified. These small notches exist in the Cassowary before the adult age ; but the end of 

 the sternum is a bluntly pointed cartilage. The long, subcultrate sternum of the Rhea 

 continues soft after its posterior third ; but the bone ends in an emarginate manner. In 

 the shorter sternum of the Emu, the xiphoid end is pointed, yet a broad margin is left 



