2-10 Annals of thf. Carnegie Museum. 



scapula of its own side, resting also a very little on the scapular process 

 of the coracoid. 



A coracoid is comparatively rather a short bone, being somewhat 

 compressed in the antero-posterior direction. Its scapular, wing-like 

 process is well produced, and is perforated by a small foramen near its 

 center. As usual, its sternal end is expanded, and an elongated con- 

 cavity occupies its inferior border, it being intended for the long con- 

 vex facette in the coracoidal groove of the sternum, which was de- 

 scribed above. There is a rudimentary epicoracoid process present. 

 Superiorly, the summit of the coracoid exhibits the ordinary tuberous 

 head, and below this for a limited distance the shaft position, irrespec- 

 tive of the scapular process, is laterally compressed. With the aid of 

 a scapula it forms, in the usual manner on either side, the glenoid . 

 cavity, which is of good size in these Ibises. A scapula has a cimi- 

 ter-like blade, which gently along its continuity is curved outwards. 

 It is smaller at its neck than it is distally, where it is obliquely trun- 

 cated from within outwards, a circumstance which gives a sharpened 

 distal apex. Its posterior portion is thin and flat, and somewhat 

 broad ; its neck is thicker. With the scapular process of the coracoid 

 it makes an extensive articulation, and mesially is overlapped with the 

 end of the clavicle. All these bones of the pectoral arch are undoubt- 

 edly pneumatic, but owing to the extreme smallness of the foramina 

 those openings are found only after careful search. 



A male Plcgadis giiarauna has a scapula 5.6 cm. long, and a cora- 

 coid 4.0 cm. high; the same bones measuring in the female 4.9 cm- 

 and 3.6 cm., respectively. In taking the lengths of the coracoids we 

 measure them from the highest point on the summit to the minutfe process 

 seen at the outer termination of the facette of the sternal extremity. 



The Pecto7'al Liin/? : As in Tantalus, so in Guara and Plcgadis, 

 the huuierus is the only pneumatic bone of this part of the skeleton. 

 In G. alba it has an average length of 10 cm., while in P. guarauna 

 it rarely exceeds 9 cm. Of course, it is relatively as well as actually 

 shorter in the females. Apart from this matter of size, the bone has 

 the same general characters as we have given them above for Tantalus. 

 In these true Ibises, however, the radial crest is better developed, and 

 its free convex border presents an unusually regular curve, resembling 

 the arc of a circle. Moreover, the expanded portion of the proximal 

 end of the bone is shorter than in Tantalus, but the single pneumatic 

 foramen holds the same position in the three genera. In a male 



