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, and D) and the Anura absorption of cartilage 

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



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

 C, Spelerpes; and D, Salamandrina. Ch. notochord ; CK, iutra-vertebral cartilage and 

 fat-cells ; Gk, convex anterior face of centrum ; Gfp, concave posterior face ; Jrl; inter-vertebral 

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

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

 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 vertebrse are said to be ophistkoccdous : 

 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 



