92 THE OSTEOLOGY OF THE REPTILES 



for the peculiar saddle-shaped articulations of the cervical vertebrae 

 of birds. 



On the dorsal side of the arch, in the middle, is the spine or neura- 

 pophysis, of extremely variable size and length, sometimes rudi- 

 mentary, sometimes very long. As a rule, the spines are longest and 

 stoutest at the beginning of the dorsal series, for the attachment of 

 muscles and ligaments controlling the neck and head. The spines 

 are always short in legless or slender crawling reptiles (Fig. 73 d-f) 

 and are never long or slender in aquatic reptiles, in front at least. 

 The spines of most sauropod dinosaurs in front of the sacrum are 

 broadly divided, V-shaped, doubtless for the lodgment of stout 

 muscles and ligaments used in controlling the long neck. 



A longer or shorter process on the sides of the arch for the support 

 in part or wholly of the ribs is known as a diapophysis (Fig. 73 b, 

 75). A like process or facet on the side of the centrum anteriorly for 

 articulation of the head of the rib is called a parapophysis (Fig. 73 f) . 

 Either is commonly called a transverse process, and the same term 

 is often applied to a like process on the sides of the caudal vertebrae, 

 of which probably the anterior ones, at least, in all cases are merely 

 coossified ribs. 



A process, paired or single, on the under side of the vertebrae, is 

 properly called a hypapophysis (Figs. 73 e, 75 a). Hypapophyses 

 are characteristic of snakes, often as far back as the tail; in some 

 instances they are developed to serve as a sort of masticatory 

 apparatus for the crushing of eggs in the stomach.^ They also 

 often occur on the cervical vertebrae of lizards, crocodiles, and 

 turtles. Paired hypapophyses (lymphapophyses) are characteristic 

 of the caudal vertebrae of snakes, where they replace the absent 

 chevrons.^ 



When the ends of the centra are concave, as they are in all early 

 reptiles, nearly all fishes, and most amphibians, the vertebrae are 

 known as amphicoelous (Fig. 74) . If the cavities are deeply concave, 

 communicating with each other through the centrum, the vertebrae 

 are called notochordal; that is, the notochord was continuous in life. 

 And this was the primitive condition found in the Cotylosauria (Fig. 



1 [The eggs are cut, not crushed, and in the oesophagus, not the stomach (Fitz- 

 simons). — Ed.] 



^ [The distinctions between lymphapophyses and hypapophyses break down in the 

 embryology of modern lizards. — Ed.] 



