XXI V] MAIN DIVISIONS 631 



from the other Game-Birds and make it the type of a primary 

 division, the Tinamiformes, but in all essentials it is a Game-Bird 

 which retains primitive characters. In one respect, however, the 

 Game -Birds are not primitive, but secondary ; they are for the most 

 part grain eaters. 



Now the primitive Birds had teeth, and we may assume that in 

 its leaps from branch to branch the ancestral reptile chased some- 

 thing more active than seeds. With great probability we may con- 

 clude that the original bird was insectivorous, and it is useful to 

 remember that this is true of the chicks of very many species the 

 adults of which are not insectivorous. 



A number of 'large flightless Birds agree with the Tinamou in 

 possessing a dromaeognathous palate and in having a penis. These 

 are grouped together as RATITAE, because the breast-bone has lost 

 its keel and has become raft-like, and the clavicles have disappeared. 

 These are secondary degenerative changes due to the loss of the 

 power of flight, and another such change is found in the loss of 

 barbules, in consequence of which the feathers have a soft downy 

 consistence. This is because they are not required to form a firm 

 surface with which to beat the air. It is this character which makes 

 them prized for ornament. 



The Ratitae include the true Ostrich (Struthid) from Africa with 

 two toes, the Rhea from South America with three toes, the Emeu 

 (Dromaeus) from Australia and the Cassowary (Casuarius) from 

 New Guinea with three toes. All these species have powerful legs 

 and can run at a great rate. Finally we have the Kiwi (Apteryx) 

 from New Zealand with four toes, the smallest Ratite Bird, but in 

 that country there formerly existed the largest of all Ratites, the 

 Moas (Dinornis), which had thigh bones thicker than those of a 

 horse. These, though now extinct, survived into the human period. 



The Tinamiformes and Galliformes, and all other Birds, are 

 grouped as CARINATAE, but this is a most illogical proceeding, as 

 individual species among them have lost the power of flight, and lost 

 in consequence, or very nearly lost, the carina or keel on the sternum. 

 And the Ratitae are certainly not descended from a common Ratite 

 ancestor, but represent different types of archaic birds which have 

 independently lost the power of flight owing to the circumstances in 

 which they have found themselves. In the Ratitae of New Zealand 

 this was certainly due to the absence of carnivorous mammals. 



Reverting now to Birds of more modern type and passing over the 

 Galliformes, we find in the group of Divers (Colymbiformes) 



