210 THE VERTEBRATE SKELETON. 



Order 8. CnocoDiLiA 1 . 



This order includes the Crocodiles, Alligators and Garials 

 and various extinct forms, some of which are closely allied to 

 the early Dinosaurs. 



There is always a more or less complete exoskeleton formed 

 of bony scutes overlain by epidermal scales ; these bony scutes 

 are specially well developed on the dorsal surface but may 

 occur also on the ventral. The vertebral column is divisible 

 into the five regions commonly distinguishable. In all living 

 forms the vertebrae, with the exception of the atlas and axis, 

 the two sacrals, and first caudal, are procoelous, but in many 

 extinct forms they are amphicoelous. The atlas (fig. 71) is 

 remarkable, consisting of four pieces, and the first caudal is 

 biconvex. 



The teeth are, in the adult, planted in separate deep 

 sockets. The skull is very dense and solid, and all the 

 component bones including the quadrate are firmly united. 

 The dorsal surface of the skull is generally characteristically 

 sculptured. There is an interorbital septum, and the orbito- 

 sphenoidal and presphenoidal regions are imperfectly ossified. 

 Supratemporal, infratemporal, and post-temporal fossae occur, 

 but no interparietal foramen. In living genera there is a long 

 secondary palate formed by the meeting in the middle line of 

 the palatines, pterygoids and maxillae (fig. 43, A). 



Cervical ribs (fig. 41, 8 and 9) are well developed, and arti- 

 culate with rather prominent surfaces borne on the neural 

 arches and centra respectively. The thoracic ribs articulate 

 with the long transverse processes, and sternal ribs and 



1 See C. B. Briihl, Das skelet der Krokodiliden, Wien, 1862. C. K. 

 Hoffmann in Bronn's Klassen und Ordnungen des Thier-reichs, Bd. vi. 

 Abth. in. 188185. T. H. Huxley, Proc. Linn. Soc. (Zoology) 1860 

 vol. iv. p. 1. E. Owen, History of British fossil Reptiles. Crocodilia 

 (Palaeont. Soc.). A. Smith Woodward, Geol. Mag. 1885, 3rd dec. H. p. 

 496. A. Smith Woodward, Proc. of Geologists' Assoc. vol. ix. p. 288, 1886. 



