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the rib increases in length in the third and fourth pairs and diminishes in the last two ; the 

 sixth rib begins to lose its breadth, and the rest become narrower to the last. The bony 

 appendages to the vertebral ribs are developed in the first seven pairs : they are articulated 

 by a broad base to a fissure in the posterior margin of these vertebral ribs a little below their 

 middle part, and, save those of the first pair, overlap the succeeding rib : these processes are 

 not anchylosed in the specimen described. The Rhea comes nearest to the Apteryx in the 

 size of these costal appendages. The first four sternal ribs are transversely expanded at their 

 sternal extremities, which severally present a concave surface lined with smooth cartilage and 

 gynovial membrane, and playing upon a corresponding smooth convexity in the costal margin 

 of the sternum, which thus presents four true enarthrodial joints with capsular ligaments on 

 each side. This elaborate structure is not, however, peculiar to the Apteryx among birds, 

 but relates to the importance of the movements of the sternal ribs, which are the centres upon 

 which the respiratory morions hinge, the angles between the vertebral and sternal ribs, and 

 between these and the sternum, becoming more open in inspiration when the sternum is 

 depressed, and the contrary when the sternum is approximated to the dorsal region in ex- 

 piration. 



The sternum the main characteristic of the skeleton of the bird is reduced to its lowest 

 grade of development in the Apteryx. In its small size, and in the total absence of a keel, 

 it resembles that of the Struthious birds, but differs in the wide anterior emargination, and 

 in the much greater extent of the two posterior fissures. 



The anterior margin presents no trace of a manubrial process as in the Ostrich : on the 

 contrary, the wide interspace between the articular cavities of the coracoid is deeply concave : 

 in the extent of this interspace the Rhea most resembles the Apteryx, but its contour is almost 

 straight ; in the Cassowary the space is narrower, but is deeply notched. The articular sur- 

 face for the coracoid is an open groove, which in the fresh state is covered with articular car- 

 tilage : external to this groove the anterior angles of the sternum are produced into two strong 

 triangular processes with the apex obtuse. The costal margin is thickened, and when viewed 

 anteriorly, presents an undulating contour, from the presence of the four articular convexities 

 for the sternal ribs and the intermediate excavations. The sternum of the Emeu presents a 

 similar appearance. The extent of the posterior notches is equal to one half the entire length 

 of the sternum : the external boundaries of these notches curve towards each other. 



The scapula and coracoid are anchylosed : a small perforation anterior to the articular sur- 

 face of the humerus indicates the separation between the coracoid and rudimental clavicle, of 

 which there is otherwise not the least trace. 



The coracoid is the strongest bone : its inferior expanded extremity presents an articular 

 convexity, adapted to the sternal groove before described. 



The scapula reaches to the third rib : it is a simple narrow plate of bone, slightly curved 

 and expanded at both ends, but chiefly at the humeral articulation. Its length is 1 inch. 



The humerus is a slender, cylindrical, styliform bone, slightly bent, 1 inch 5 lines in length ; 

 slightly expanded at the two extremities, most so at the proximal end, which supports a trans- 

 verse oval articular convexity, covered with smooth cartilage, and joined by a synovial and 

 capsular membrane to the scapulo-coracoid articulation. A small tuberosity projects beyond 

 each end of the humeral articular surface. The distal end of the humerus is articulated by 



