BIRDS. 159 



magnified one and a half diameters) the Shoulder-bones and Sternum of a recently hatched 

 Mantchourian Crane (Grus montignesia) : for the structure of the adult Cranes I must refer to 

 the specimens in the Hunterian and British Museums. 



The scapula (fig. 0, sc.) is long and ensiform ; it is soft at its glenoid (gl.) and supra- 

 scapular (s. sc.) regions. The coracoid (cr.) is moderately long ; its head is large and round, and 

 its epicoracoid base (e. cr.) is large and semilunar ; these parts are still unossified. One very 

 important character of the Crane's coracoid is the large development of the meso-coracoid (m. cr.) ; 

 it is not so large, relatively, in the embryo as in the adult, as it receives much increment from 

 the periosteal layers ; here it is seen to be soft down to the foramen (cr. f.), but it is ossified from 

 the main shaft, below. The clavicles (cl.) receive but little augmentation from the meso-scapular 

 and prse-coracoid segments ; their main part (cut away in fig. 6, to show the Sternum) is a 

 slender rod in the early stage ; below they have coalesced with the pointed inter-clavicle. 

 Already this part (i. cl.) is wedged in between the halves of the sternal keel, at the angle (k.), ready 

 for the complete coalescence of these parts, which takes place in the adult Crane. Moreover, this 

 occupation by the inter-clavicle of the primordial sternal fissure is what we have already seen in 

 certain Lizards where the Sternum is always flat and keelless (see Plate IX, figs. 8, 9). As the 

 lateral parts of the Sternum chondrify before the middle (or ento-sternal), they may, as to time, be 

 said to be primary, and the mid-portion secondary ; and if these secondary parts, namely, the 

 rostrum (r.), the lower coracoid lip defining the groove (cr. g.), the keel (k.), and the middle 

 and intermediate xiphoid processes (m. x., i. x.), had not as yet been developed, then the 

 Sternum would have been composed of two narrow bands, diverging from each other, both before 

 and behind. Behind their connection with the perfect costal arches these bands approach each 

 other, but further backwards (e. x.) they diverge very much, and this divergence is precisely that 

 which obtains in those Reptiles (Stettio and Crocodilus, see Plate XI, figs. 2 and 8, x. st.) that 

 have free xiphisternal horns. 



At present the rostrum (r.) is a small projecting papilla, and the coracoid grooves (figs. 

 6 8, cr. g.) meet at an acute angle, and overlap, so that the right coracoid passes beneath the 

 left for a small distance. 



The keel (k.) occupies merely the middle third of the Sternum, a little nearer the end than 

 the front; it is a sharp, flat crest (fig. 7, k.), and its angle is produced forwards as two 

 distinct narrow flaps, that embrace the inter-clavicle (i. cl.). In front of the keel there is a 

 lanceolate fossa (fig. 6, f.) ; this is a correlate of the upward curve of the trachea. There are 

 seven pairs of lateral papilla?, which will be converted into costal condyles (fig. 7, c. c.) ; the 

 sternal ribs (the first of these, s. r. 1., is shown in fig. 6) are still soft. 



Amongst the skeletal parts of Grus antigone in the Hunterian Museum (' Catal.,' vol. i, 

 pp. 246 and 247, Nos. 1319 1332), there is the Sternum of a half-grown bird; in it there may 

 be seen a large, ovoidal scooped space, some distance below the rostrum ; this invades the front 

 of the Sternum, and is a development of the fossa shown in Plate XIV, fig. 6, f. In this more 

 advanced stage the inter-clavicle only articulates with the projecting keel, and the tracheal loop 

 turns suddenly upwards, apparently causing non-development and absorption of the bone nearly 

 to the lower coracoid lip. 



The front of the keel is scooped at this second stage, but it is thick behind the vertical fossa, 

 and then for the rest of its extent is flat, as in other Birds. In the adults, however, the trachea 

 has passed along, inside, to the extreme end of the keel, which bulges upwards into the thoracic 



