66 



COMPARATIVE ANATOMY 



axis in the position usually occupied by dorsal ribs : thus these 

 forms are ribless, and also in certain Teleosts and Ganoids the ribs 

 are wanting (e.g. Lophobranchii) or quite vestigial (Polyodon). 



Amphibians. The ribs in the Amphibia correspond to the 

 dorsal ribs of Fishes, and are alwaj's connected with transverse 

 processes or at any rate with the vestiges of the basal stumps 

 (Fig. 50, F). The latter arc originally situated, as in Fishes, 

 towards the ventral side of the vertebral axis, nnd in the tail give 



B 



FIG. 52. A, VERTEBRA FROM ANTERIOR PART OF TAIL OF LARVA (43 MM.) 

 OF Nc<-tiiru$\ B, SACRAL VERTEBRA FROM LARVA (43 MM.) OF Nedum*; 

 C, FOURTH TRUNK-VERTEBRA FROM NEWLY-BORN LARVA OF Salanwiuli-n 

 maculosa. (After Goppert. ) 



Art. n/i., vertebral artery ; B, cartilage of basal stump ; B 1 . vestige of same in 

 larva of Salamander; B'*, bony bar which replaces the same functionally ; 

 Ch, notochord ; DRX, dorsal bar of ril> : .//. ilium ; N, neural arch ; /.'. rib ; 

 RT, A'7' 1 , ventral and dorsal rib-bearing portions of vertebra ; .s'/- 1 , lateral 

 process of hamial arch (//). 



rise to haemal arches (Necturus, Salamander-larvae). In connection, 

 apparently, with the more dorsal position of the horizontal inter- 

 muscular septum in which they are situated, the transverse 

 processes, even in Salamanders, tend to arise more from the neural 

 arches than from the centra, and this upward displacement is carried 

 still further in the Gymnophiona and Anura. In TJrocleles (Fig. 

 52) the cartilaginous, rib-bearing basal stump is in close connection 

 with the centrum, but gives off secondarily an upwardly directed 



