Aves — Classification. 97 



The presence of teeth, either in grooves or sockets, is seen 

 tu be common to all the earlier members of the class Aves. 



Of the first sub-class only a single representative, Archoeop- 

 teryx, is known : this is from the Upper Jurassic of Germany. Of 

 division A of the second sub-class likewise only one represen- 

 tative, Hesperornis, has been discovered : this is from the 

 Cretaceous of Noith America. Section B includes Tertiary and 

 recent raft-breasted* birds except those which like the Dodo and 

 Cvemiornis, can be definitely referred to some Carinate group. 

 The Ostrich and Emeu, Dinornis and JEpyornis, are examples of 

 birds belonging to this section. 



The third sub-class includes the vastly greater number of 

 birds. The Eagle, Duck, and Crow may be taken as examples. 

 The great majority of the Garinatrr can fly, but, as already men- 

 tioned, certain members of the sub-class such as the Dodo, Soli- 

 taire. Cnerniomis, Aptomis, and Aphanapteryx, have lost their 

 power of flight. Such birds are usually the inhabitants of 

 islands where there are no carnivorous mammals to prey upon 

 them, so that having little necessity for flight, their wings 

 become reduced through disuse. Of all enemies the most des- 

 tructive to these helpless birds is man, and it is through his 

 agency that the Dodo, Solitaire, and many others havp become 

 extinct. The occurrence of such groups of reduced Carinates is 

 probably not confined to recent times, but instances of it may 

 frequently have happened in the past. The Stereornithes (of 

 which PhororJiacos and Brontornis may be taken as examples ; 

 see Wall-case 25) from the (?) Miocene of South America, and 

 the Gastornithidce from the Eocene of Europe, are probably 

 examples of such groups. 



* This form of breast-bone has been independently acquired in many groups 

 of Carinate birds : it is by itself of little or no value for classificatory purposes, 

 being merely correlated with the loss of power of flight. 



[Explanatory note to letters on figure of Archaeopleryx macrura, p. 88. 



Fig. 112. — b, east of brain-cavity of cranium (the dark object to the left 

 of f, is part of maxilla) ; c, c, ribs ; fu, furculum ; sc, scapula; 

 h, h' humeri ; r, r', radii ; u, u', ulna? ; cr, carpals ; 1, 2, phalangeals 

 of man us ; i, ischium ; a, acetabulum: f,f femora ; t, t', tibia; ; ml, 

 tarso- metatarsal bone; p, phalanges of pes.] 



(1876) h 



