180 CHORD AT A. 



Class V. Aves. Birds. 



Feathered warm-blooded vertebrates with lungs closely adherent to 

 the back of the thorax and communicating with air-sacs which extend 

 between the viscera and into the bones. Ventricle completely divided, 

 the right auriculo-ventricular valve muscular, and a single aortic arch 

 curving to the right. Occipital region with a single condyle, numerous 

 vertebrae fused to form a pseud-sacrum, fore-limbs wings, pelvis with fused 

 bones, and (as a rule) neither pubic nor ischial symphyses, ankle-joint 

 between a tibio-tarsus and tarso-metatarsus. Eight ovary and oviduct 

 rudimentary ; oviparous. Some toothed fossil forms. 



Order 1. Saururce. Numerous free caudal vertebrae ; jaws with teeth. 

 Archaeopteryx lithographica from the Upper Oolite. 



Order 2. Ratitce (Cursores). Wings rudimentary, no keel to the 

 sternum. 



Dinornis, extinct moa of New Zealand. Struthio camelus, ostrich, 

 Deserts of N., E., and S. Africa, Arabia, and Syria. Rhea Americana, 

 S. America. Dromseus, emeu, Australia. Casuarius, cassowary, New 

 Guinea, &c., and N. Australia. Apteryx australis, with complete dia- 

 phragm and air-sacs situated in the thorax; New Zealand. Odontolcae, 

 with teeth in grooves. Hesperornis, from the Cretaceous. 



