278 



ZOOLOGY 



SECT, 



more perfectly developed than in any Fish, and have well-formed 

 zygapophyses, which articulate with one another by synovial 

 joints. 



The Gymnophiona also have biconcave vertebrae, but in the higher 

 Urodela (Fig. 891, G and D) and the Anura absorption of cartilage 

 takes place between adjacent centra in such a way that the convex 



-liaf 



FIG. 891. Longitudinal sections of vertebral 'centra of A, Ranidens; B, 



C, Spelerpes; and D, Salamandrina. Ch. notochord ; CK, in tra-vcrtebral .cartilage and 

 fat-cells ; Gk, convex anterior face of centrum ; Cfp, concave posterior face ; JvK\ inter-vertebral 

 cartilage ; K, superficial bone of centrum ; Ligt. inter- vertebral ligament ; Mh , marrow-cavity ; 

 R, transverse process ; S intra vertebral constriction. (From Wiedersheim's Comparatin 

 Anatomy.) 



end of one fits into the concave end of the next, forming a 

 cup-and-ball joint. In the higher Urodela the convexity is on 

 the anterior, the concavity on the posterior face of each 

 centrum (D), and the vertebra are said to be ophisthoccelous : 

 in the Anura they are usually, as in the Frog, procoelous. 

 In the Stegocephali there is great diversity in the structure 

 of the vertebral column. There may be well -developed 

 dice-box-shaped centra, or the neural arches may be simply 



