M 



URODELA 



All the trunk -vertebrae, with the exception of the atlas, 

 carry ribs, at least vestiges thereof. Owing to the early tlis- 

 appearance of the basiventral cartilages the capitular portions of 



the ribs are much reduced, and 

 are mostly represented ))y strands 

 of connective tissue only. Tlie 

 ribs develop therefore occasion- 

 ally at some distance from the 

 vertebral column, and that por- 

 tion of the rib which in the 

 metamorphosed young newt looks 

 like the capitulum is to a great 

 extent really its tuberculum. 

 Witness the position of the ver- 

 tebral artery, which still indi- 

 cates the true foramen trans- 

 versariiun. The homologies of 

 these parts are still more ob- 

 scured by the fact that a new 

 process grows out from the rib, 

 by which the latter gains a new 

 support upon a knob bf the 

 neural arch. Thus an additional foramen is formed, sometimes 

 confounded with the true transverse canal. The meaning which 

 underlies all these modifications is the broadening of the body, 

 tlie ribs shifting their originally more ventral support towards 

 the dorsal side. The whole process is intensified in the Anura ; 

 it is an initial stage of the notocentrous type of vertebrae. The 

 transverse ossified processes of the adult are often much longer 

 than the vestiges of the ribs themselves, and are somewhat com- 

 plicated structures. They are composed first of the rib-bearing 

 cartilaginous t3utgrowths of the neural arches ; secondly, of a broad 

 string of connective tissue which extends from the ventro-lateral 

 corner of the perichordai sj^eletogenous layer to the ribs. 



The shoulder-girdle is extremely simple. It remains almost 

 entirely cartilaginovis, and the three constituent elements are not 

 separated by sutures. Ossification is restricted to the base of the 

 shaft of the scapula, and may extend thence over the glenoid 

 cavity. The coracoids are broad, loosely overlap each other, and 

 are " tenon and mortised " into the triangular or lozenge-shaped 



Fig. "I. — Transverse section througli a 

 trunk - vertebra of a larva of Stda- 

 iiiandra maculosa, enlarged. The right 

 side shows the actually existing state, 

 while on the left side the rib and its 

 attachments are restored to their jiro- 

 bable original condition. ^1, Verte- 

 bral artery within the true transverse 

 canal ; B. V, remnant of the basi- ventral 

 cartilage ; Ch, chorda dorsalis ; Sji.c, 

 spinal canal : *, the false transverse 

 canal. 



