3 8 4 



THE ANIMAL KINGDOM. 



e. g. Crocodilia. The cervical ribs of Chelonia are simple nodules which are 

 either fused to the vertebrae, or united to them by suture. Their dorsal 

 ribs are attached between the centra of adjoining vertebrae. The dorsal 

 ribs when a sternum is present may be divided into a vertebral, inter- 

 mediate, and sternal section, e. g. Crocodilia, many Lacertilia ; or into ver- 

 tebral and sternal only : or, when the sternum is either absent (Ophidia, 

 some serpentiform Lacertilia, Chelonia, Plesiosauria, Ichthyosauria) or rudi- 

 mentary, they remain undivided. In the Chamaeleons and Gecko, some 

 of the post-sternal dorsal ribs are continuous ventrally. The sacral ribs are 

 usually massive and expanded distally, the caudal anchylosed to the verte- 

 brae. So-called abdominal ribs are found as ossifications of the intermus- 

 cular septa (Crocodilia) or of the subcutaneous fibrous tissue (Hatteria). 

 The sternum is present but is very small and rudimentary in some 

 serpentiform Lacertilia : in some other Lacertilia, e. g. Acontias meleagris, 

 its right and left halves are stated to remain separate : in others again its 

 bilateral origin is evidenced by a median fontanelle, and by the prolongation 

 backwards, as occurs also in Crocodilia, of two xiphisternal horns with which 

 a certain number of ribs articulate. It is generally more or less rhomboidal 

 in shape, cartilaginous and partially ossified in substance. In many 

 Deinosauria, e. g. Brontosaurus, Iguanodon, there are two sternal bones 

 which were either joined by cartilage or had each a separate cartila- 

 ginous border. The sternum of Pterodactyles is well ossified, the cartilage 

 probably replaced by membrane bone, and there is a median keel to the 

 ventral surface. 



The shoulder-girdle and fore-limb are absent in Ophidia, but in serpen- 

 tiform Lacertilia the former is present when the limb is absent. There is a 

 scapula and coracoid, the latter articulating with the sternum. The scapula 

 generally possesses a dorsal cartilaginous but partially ossified supra- 

 scapula, the coracoid a similar but ventral epicoracoid. In many Lacertilia, 

 where the bones are broad, there are membranous tracts forming fenestrae, 

 especially in the coracoids : and the epicoracoids overlap one another 

 anteriorly. The scapula and coracoid are anchylosed in the gigantic 

 Pteranodontia among Pterodactyles, and the scapula articulates with the 

 neural spines of several anchylosed vertebrae, a unique feature among Ver- 

 tebrata.' The clavicle is absent in Chelonia, Crocodilia, Chamaeleons, &c., 

 in some Deinosauria, if not in all, and in Pterodactyles. It is continuous 

 with the scapula in Chelonia, forming a large stout bone : separated from 

 the scapula and slender in other groups. There is an interclavicle or 

 episternum in Crocodilia : it is large and T-shaped in Lacertilia and 

 Ichthyosauria, and the two clavicles are closely connected with its anterior 

 border. There is no trace of a pelvis nor of hind-limb in the majority of 

 Ophidia, but the Typhlopidae, Tortricidae and Pythonidae have both a 

 rudimentary ischio-pubis and limb. In the serpentiform Lacertilia there 



