160 SHOULDER-GIRDLE AND BREAST-BONE. 



cavity behind ; grows into a bony box, which is continuous with the rostrum, in front ; whilst at 

 the angle complete coalescence has taken place with the interclavicular part of the furcula. 



In outline the Sternum has become long-oblong, and the posterior margin has an almost 

 transverse outline, the elegant but small notches of the embryo having become converted into 

 gentle sinuosities. 



In Balearica the furcula is less V-shaped than in Grus; it does not reach the angle of 

 the sternal keel, which is not produced so much forwards; the Sternum is neatly oblong, 

 a little broader in front than behind; the hinder margin is gently trilobate, and a trace 

 of the "intermediate notch" is seen on the middle lobe, on each side; in this genus the trachea 

 does not enter the keel, and the keel itself scarcely reaches the end of the Sternum. 



In Psophia (see ' Catal. Hunt. Mus.,' vol. i, p. 248, No. 1343) these parts are intermediate 

 between those of the embryo of the typical Grus and the adult Balearica. 



The scapula of Psophia (Plate XIV, fig. 9, sc.) is considerably curved, unusually broad, and 

 has a strong, blunt, out-turned acromion process. In Rhinochetus the scapula has a similar shape, 

 but it is altogether smaller and more bent, being a very rudimentary form. In Eurypyga the scapula 

 is almost tne exact counterpart of that of Psophia. The coracoid of Psophia (Plate XIV, fig. 9, cr.) 

 agrees with that of the typical Cranes ; the meso-coracoid plate (m. cr.) having a unique develop- 

 ment for a Bird, and the coracoid foramen (c. f. m.) is nearer the posterior -than the front margin 

 and the bone. In Rhinochetus the coracoid is long and slender, and the meso-coracoid ledge of 

 bone becomes narrow in the middle, but never dies out ; in neither of these types is there any- 

 thing more than a rudiment of the epicoracoid hook. In Eurypyga the coracoid approaches that 

 of the Pluvialinas, but, nevertheless, the meso-coracoid ridge is continuous along the inner side 

 of the bone, although narrow ; the epicoracoid hook is large. The furcula of these species is very 

 instructive; in Psophia and in Eurypyga it comes close to that of the Pteroclinse, answering 

 very exactly to that of a young Plover ; yet in it Psophia is more V-shaped, and in old age the 

 inter-clavicular bar is nearly as well developed as in the Gallinacese ; and the thick tip of each 

 ramus is caused, as in them, by the solid ossification of a lump of cartilage the " meso-scapular 

 segment." In Eurypyga, as in Pterocles, the inter- clavicle is a small tubercle, like that of an 

 embryo Plover, and the rami of the furcula are bent backwards, and not so much thickened by 

 the cartilaginous segment. The furcula of the Kagu (Rhinochetus) is intermediate between that 

 of a Tinamou and a Rail ; it is long, and U-shaped ; the tips of the rami are curved backwards, 

 and, as in those types, there is no trace of an inter-clavicle : it answers to the furcula of the Plover, 

 before the inter-clavicle appears. The Sternum of Psophia is exactly intermediate between that 

 of the embryo Crane (Plate XIV, figs. 6 8) and that of Balearica. The Sternum of the Kagu 

 is arrested at an earlier stage than what is seen in the ripe embryo of the Crane ; for the rostrum 

 is absent, and the anterior margin shows the primordial notch as in Brachypteryx and Apteryx 

 (see Plate XVII, fig. 1) ; its keel also is in a similar state of arrest. In Eurypyga the outer 

 xiphoid notch is almost as much developed as in Himantopus ; the rostrum is equal to what is 

 seen in the true Ardeinae ; the keel is intermediate between that of a Plover and the Psophia -, 

 but, as in the latter form, it is pneumatic and not oily, as in the true Plover. A rare and 

 unique notch appears at the end of the keel, tending to separate it from the body of the bone. 1 



1 I have no room here for further detail as to this instructive group of ancient types of the Grallae ; 

 but the osteology of the Kagu and its relations will' be explained and illustrated in a paper by me, 

 soon to appear in the ' Zoological Transactions.' 



