OSSEOUS SYSTEM OF AVES. 



21 



perforated, are afforded by Swifts, Humming-birds, iig. 18, some 

 Eagles {Aqidla, Pandion, HalicBtus) and Petrels ( Thalassidroma), 

 in connection with excessive developement of the bone and great 

 powers of flight ; also by the Emeu, Rhea, Cassowary, and Notor- 

 nis, fig. 16, where the bone stops short of the parts exhibiting the 

 notches or grooves in birds of flight, and retains almost the small 

 lacertian proportions, fig. 17, a. The oblong and not very large 

 sternum of some Cockatoos {Cahjiytorlujnclms) is entire; in the 



16 



17 



Cursorial steniuni, Notoniis. 



Lacertiau sternum, Iguaua. 



Balearic and Demoiselle Cranes, in the Ibis ( Tantalus Ibis) ; in 

 the Agami [Psophia), the sternum is long, narrow, and entire. 

 The broad sternum of the Frigate-bird ( Tachypetes) and the long 

 sternum of the wingless Auk (Alca impc?inis) are also entire.^ 



The anterior margin of the sternal body is impressed by the arti- 

 cular ca\^ties for the coracoids. In Notornis, fig. 16, b, Dinornis 

 and Apteryx they are small shallow depressions, near the outer 

 angles : they are similarly situated, but longer and deeper, in the 

 Rhea and Cassowary ; are more extended and with a sliorter inter- 

 space in the Ostrich. In birds of flight they are deep grooves, 

 with the upper or hinder border thickened and convex in many, 

 affordino; a concavo-convex surface for the broad end of the coracoid. 

 They mostly meet at the midline; they are continuous, perforating 

 the base of the manubrium, in some Gallince (Perdix) ; and have 

 their medial ends decussating, extending one in advance of the 



' xn: 



