55 6 FLIGHTLESS BIRDS. 



like or uncinate processes of the ribs are never more than three in number, and are 

 often rudimental, or even absent. In addition to the agreement in the structure 

 of the skull, they resemble the tinamus in that the terminal vertebrae of the tail 

 are not united to form a ploughshare-like bone. 



On account of the invariable absence of a keel to the 

 breast-bone, this group of birds, which includes the ostrich 

 and its allies, are collectively designated the Ratitce or 

 Katites so named from the Latin term for a flat-bottomed 

 boat. This group is reckoned as a subclass of equal rank 

 with the Carinatce ; and by many ornithologists is subdivided 



KEEL-LESS BREAST-BO OF into orders, although we shall content ourselves by arranging 

 A RATITE BIRD. its various members in families. The existing members of 



the group, which are comparatively few in number and have 



a remarkably scattered distribution on the surface of the globe, are widely different 

 from one another in structure, and include the largest of all birds, while none 

 of them are very small. Very different views have been entertained as to the 

 relationship of these Ratite birds to the Carmates ; it having at one time been 

 supposed that the former might represent the ancestral stock from which the latter 

 was derived. There is, however, now a pretty general consensus of opinion that 

 the Ratites are derived from flying, and consequently Carinate birds, and that 

 the tinamus are their nearest living allies. 



THE OSTRICHES. 

 Family STEUTHIONIDJE. 



The ostriches are the largest of all existing Ratites, and therefore of all living 

 birds, and they are at the same time the most specialised representatives of the sub- 

 class ; this specialisation showing itself in the reduction of the number of toes to two, 

 owing to the absence not only of the first or hind-toe, but likewise of the second. 

 In this respect ostriches are perfectly unique among birds. While they agree with 

 the majority of their allies in their short beak, ostriches are further characterised by 

 the short stunted nails on the toes, the great proportionate length of the humerus 

 of the rudimental wing, and the absence of after-shafts to the feathers. In the 

 skeleton the furcula is wanting, the pubic bones of the pelvis unite in a symphysis 

 (as they do in many reptiles but in no other birds), and the lower end of the tibia 

 has no bony bridge over the extensor tendons ; while there are also certain 

 characteristic features in the base of the skull, into the consideration of which it 

 will be unnecessary to enter. In addition to their large size and two toes, 

 ostriches are characterised externally by the small and flattened head, in which 

 the short beak is broad and depressed ; the long, powerful, and practically naked 

 neck ; the full and massive body, provided with short wings ; the muscular and 

 partly bare thighs ; and the stout metatarsus and foot. The beak has a very wide 

 gape, reaching back to the line of the eyes ; and the nostrils open near the middle 

 of its length. The third toe is much larger than the fourth, and both are 

 furnished with soft fleshy pads on the under surface. In the immature state the 



