CHAPTER II 



THE VERTEBRAE 



The spinal column or backbone of reptiles, as of all other air-breath- 

 ing vertebrates, is made up of a variable number of separate seg- 

 ments called vertebrae. A vertebra (Fig. 73 b) is composed of a body, 

 or centrum, and an arch, or neurapophysis, each ossifying separately 

 and uniting at variable times, the neurocentral sutures more persis- 

 tent than in most mammals, young or aquatic reptiles always (Fig. 

 87 B, c), adult land reptiles often showing them.^ 



Fig. 73. Anterior dorsal and cervical vertebrae: A, B, Sphenodon (Rhynchocephalia), 

 anterior dorsal from the side and front; C, D, Iguana (Lacertilia), anterior dorsal from 

 the side and front; E, F, Ophidia, anterior dorsal from behind and in front; G, Pter- 

 anodon (Pterosauria), cervical from the side, after Eaton. 



Projections from the vertebrae, called processes or apophyses, 

 serve for the attachment of muscles or ligaments, for articulation 

 with adjacent vertebrae, or for the support of ribs, and are often 

 characteristically different in different reptiles. Two pairs of proc- 

 esses springing from the arch, one in front and one behind, are 



' [For the modern embryological viewpoint of the composition of reptilian vertebrae 

 see Schauinsland, in Hertwig's Handhuch der Entwickeluiigsgesc/ii elite der Wirbel- 

 tieren, etc., 1906. — Ed.] 



