IV. VERTEBRATA: AVES, CARINAT^E. 613 



and ill that, together with the lack of flight, many structures 

 normally connected with it are absent. The bones are but slightly 

 pneumatic, the sternum has no keel, and a furcula is not formed, 

 the clavicles being rudimentary (Dromceics) or not present as dis- 

 tinct bones. The wings are small and lack primaries and seconda- 

 ries adapted for flight, for typical contour feathers with close 

 vanes, as well as typical down feathers, are absent. 



Since several structures apparently adapted for flight occur here 

 (fusion of hand bones and often of caudal vertebra; arrangement 

 of wing muscles), it is probable that the Eatites have descended 

 from carinate forms bjr loss of power of flight. The anatomical 

 distinctions between the various families lead one to believe that 

 they have arisen from different groups of carinates and hence do 

 not form a natural assemblage. 



Section I. STRUTIIIONES, with long humerus, long legs and neck. 

 Struthionid^e, two-toed ostriches of Africa, Struthio camelus. RheiDjE, 

 South American three-toed ostriches, Rhea ameticaiia, nandu. Section 

 II. CASUAPJNA ; three toes, humerus short. Divmaus, emus; Casu- 

 arius, cassowaries. Section III. APTEEYGES, bill long, nostrils near the 

 tip, rudimentary wing skeleton; four toes. Apteryx,Y).\'!\, of New Zealand. 

 The DiNORNlTHiD^, three toes, wing skeleton absent ; giant birds (thirteen 

 feet high) of New Zealand; now extinct, but apparently contemporaneous 

 with man. The jEpiornis, a gigantic bird of Madagascar, possibly belonged 



Order IV. Carinatae. 



The name refers to the presence of the keel to the sternum, 

 which is correlated with the powers of flight possessed by most 

 species. Other characters of the class are the presence of rectrices 

 and remiges on tail and wings, and the fusion of clavicles to a 

 furcula. There are strong fliers, like the raptores and albatrosses, 

 which have but a small carina ; in many poor fliers the carina may 

 be entirely absent. The furcula is not always present, the clavicles 

 not uniting (many parrots and toucans) or being absent {Mesites). 

 The remiges are also degenerate in some carinates, as in the pen- 

 guins (which are flightless, although they have a strong carina), 

 where they take the shape of small scales. Thus the distinctions 

 between ratite and carinate birds vanish in places. 



Sub Order I. GALLINACEA. The hendike birds are praecoces with 

 compact bodies and well-developed wings and legs, so that they run and 

 fly well without excelling in either direction. The feet have three toes in 

 front, usually connected by a membrane at the base (tig. 643, c); the fourth 

 toe is behind and at a higher level. Above this in the male is usually the 



