THE ORDERS OF AVES AND REPTILIA. 105 



The long axes of^the adjacent parts of the coracoid and 

 scapula are parallel or identical. The barbs of the feathers are 

 disconnected. The diaphragm is better developed than in 

 other birds. 



The Ostriches, Eheas, Emeus, Cassowaries, and the Apteryx, 

 are the existing members of this order. 



3. CARESTAT^E. The metacarpal bones are ankylosed, and the 

 tail is shorter than the body, as in the Eatitse, the terminal 

 vertebrae being commonly ankylosed into a ploughshare-shaped 

 bone. 



The sternum possesses a crest or keel, and ossifies from a 

 median centre in that keel, as well as from paired centres. 



The long axes of the scapula and coracoid make an acute or 

 slightly obtuse angle. The barbs of the feathers are usually 

 connected. 



To this order all ordinary birds belong. 



The members of the class KEPTILIA may be grouped into 

 the following orders : 



1. The CROCODILA. These reptiles have an epidermic 

 exoskeleton consisting of horny scales, and a dermal exoskeleton 

 of bony scutes, which may be confined to the dorsal surface 

 of the body, or exist on the ventral aspect as well. 



The centra of the dorsal vertebra are procoelous or amphi- 

 ccelous ;* and in the middle and posterior dorsals a single trans- 

 verse process supports both the capitulum and the tuberculum of 

 the rib. Some of the ribs are provided with uucinate processes. 



There are two sacral vertebrae. False ribs are developed 

 as superficial ossifications in the wall of the abdomen. 



The bones of the skull and face (except the mandible and 

 hyoid) are solidly united together, and the presphenoidal 

 region, which remains cartilaginous, is flattened laterally, so 

 as to form an interorbital septum. 



The nasal passages are shut off from the mouth by palatine 

 plates of the maxillae and palate bones, and (in modern 

 Crocodiles) of the pterygoids as well. The tympanic cavities 



* Proccelow, concave in front, and convex behind. Amphicoelous, concave on 

 both faces. 



