8 BIRJ) GALLERY. 



the palatine, but forming a close union either by fusion or by over- 

 lapping suture with the base of the vomer. 



The majority of the members of this group have become flightless, 

 a fact which has brought about many modifications of the skeleton 

 and feathers. The Tinamous alone have retained the power of 

 flight. 



The Ratitse are divisible into seven Orders, probably derived from 

 three distinct stocks. Each Order can be readily defined, and presents 

 one or more points which indicate extreme specialization. 



On account of the structure of the palate, the members of this section 

 may be regarded as the most primitive of living birds. 



The seven Orders of the Ratitse are the following : 



1. Struthioniformes . One genus, Struthio. 



2. Rheiformes Two genera, Rhea and Pterocnemia. 



3. Dinornithiformes ) _ T 



. . , . > Numero us genera. Extinct forms. 



4. ^Bpyornithiformes ) 



5. Casuariiforrnes ... Two genera, Casuarius and Dromaus. 



6. Apterygiformes . . . One living genus, Apteryx, and two 



extinct genera. 



7. Tinamiformes ,.. Numerous genera. 



The characters by which the Orders are distinguished are fully 

 explained in the table-case in the first bay. 



Order 1. STRUTHIONIFORMES. OSTRICH-TRIBE. 

 in Bay.jj 



Though closely allied to the Rheas, which they resemble in general 

 appearance, the members of this order may be at once distinguished 

 from all others by possessing only two toes. Of these the one corre- 

 sponding to the middle of the three anterior toes in ordinary birds (the 

 third of the complete set) is much the largest and supports the greater 

 part of the weight. It bears a stout pointed nail. The smaller outer 

 (or fourth) toe often wants the nail. The whole of the head and neck 

 as well as the legs are bare, or only covered with short down. The body- 

 feathers are single, having no aftershaft, and the feathers of the wings 

 and tail (corresponding to the ' remiges ' and 'rectrices* of ordinary 

 birds) are of considerable size, but soft and plumose. 



Family STRUTHIONID^E. OSTRICHES. 



The Ostriches, the largest of living birds, are represented by the 

 single genus Struthio, which contains at least four living species 



