162 SHOULDER-GIRDLE AND BREAST-BONE. 



than those of the Psophia and Eurypyga : straight, slender clavicles generally go with feeble 

 wings ; but the Pigeons are notable for being exceptional in this respect. 



The Sternum of the Gallinule is very elegantly formed (see Plate XV, fig. 4), the anterior 

 part being narrowed more and more to the last sternal rib, and then the external xiphoids (e. x.) 

 becoming gently curved out and then incurved ; the middle xiphoid (m. x.) is much shorter than 

 the outer bars, and narrows to a point. There is no room for an inner notch, and the outer 

 is very deep and reaches nearly to the costal region ; in that part there are six pairs of condyles 

 (c. c.), the normal number for a Ralline Bird. The keel (k.) is a good distance from the anterior 

 margin, on which there is, at present, no rostrum, and the keel itself is very slight. In the old 

 bird there is a shallow notch between the upper coracoid lips, and a small, carinate, tongue-like 

 rostrum ; the whole Sternum becomes relatively much narrower, and the xiphoid region much longer 

 in proportion to the costal. The costal processes of the adult are more produced and sharper ; 

 the keel has become moderately deep ; the external xiphoids diverge much more behind, enlarging 

 the notch, and they and the middle xiphoids have become somewhat dilated near the end, and 

 do not ossify entirely. The anterior third of the keel, in the specimen before me, is partly 

 separated from the rest by a small fenestra. 



The Sternum of Tribonyx mortieri (Hunt. Mus., No. 1281) is in form, almost the exact 

 counterpart of that of the embryo Gallinule ; it has, however, a very small rostrum, and it has 

 relatively a deeper keel ; its furcula is strong for a Rail. The Coot (Fulica atra) has a broader 

 Sternum than the Gallinule, and its external xiphoids projects so much that it is intermediate in 

 form between that of the Land Rail and that of the Grebe (Podiceps} ; see Plate XIV, figs. 4, 5. 



In the Crake (Crex pratensis] the Sternum agrees with that of the Gallinule in its parts, 

 but it is much narrower, and the xiphoid notch is a very narrow slit. In Brachypteryx australis 

 (Hunt. Mus., No. 1280) the Sternum has much the same relative breadth as in Crex ; but in 

 the latter form the external xiphoids diverge, whilst in Brackypteryx they cling close to the 

 deeply emarginate middle part. Here, also, the rostrum is absent, so that this most elementary 

 Sternum, deeply emarginate before and behind, is in all essentials, just like that of Podiceps. 

 The Sternum of the PorpJiyrio agrees on the whole with the Gallinule, but it is much more 

 pinched in the costal region, which is relatively longer ; its external xiphoids are much broader 

 and more expanded terminally, but they retain the incurved condition seen in the embryo of the 

 Gallinule. In Ocydromus australis the scapulae are shorter and more dilated at their supra- 

 scapular end ; the furcula, like that of Bracliypteryx, is extremely slender towards the angle, and 

 the Sternum is like what is seen in that species, save that it has a slight rostrum, a smaller 

 emargination behind, freer external xiphoids, and these bars have pedate cartilaginous ends; 

 the keel, also, is more developed. If the important sternal fragments figured in Professor 

 . Owen's valuable paper on Cnemiornis ('Trans. Zool. Soc.,' 1866, vol. v, p. 63, figs. 5 9) belonged 

 to the same species as the leg bones, then there have been Rails with a Sternum intermediate in 

 carination between that of a Rhea and an Emeu. 



