408 ZOOLOGY. 



in such a way that the tail feathers (rectrices) are arranged 

 in a semi-circle (or sometimes wanting). Teeth are wanting 

 except in some extinct forms, which stand intermediate be- 

 tween the Saururae and the recent birds. 



Division I. Ratitce. These are running birds with a flat 

 breast bone (i. e., no keel) and with all the organs of flight 

 much reduced. The barbs of the feathers are not held to- 

 gether by barbules, thus producing plumes. 



FIG. 209. 





FIG. 209. Wood Duck (Aix sponsa). Photographed by Dr. J. W. Folsom. 



The Ratitae (order Cursor -es) are the lowest forms of living 

 birds and include the ostriches, emus, cassowaries, in all of 

 which the wings are reduced, and the Apteryx or wingless 

 bird of New Zealand (Fig. 207) in which they are very rudi- 

 mentary. The ostrich (Fig. 208) is the largest and most pow- 

 erful of living birds. Ostriches are somewhat gregarious, and 

 frequent regions more or less desert. At mating time they 

 unite in pairs, the male assisting in incubating the eggs, which 



