2 7 6 



TELEOSTOMI 



the girdle is ossified, except in Amia and the Chondrostei. A 

 bony coracoid appears below, and a bony scapula above, generally 

 pierced by a large foramen. In all the lower sub-orders, and in 

 some of the less specialised Teleostei, we find a third inner 

 anterior process differentiated from the coracoid, known as the 

 mesocoracoid (precoracoid of Parker [317], Fig. 243), which may 

 be separately ossified. This mesocoracoid arch, although absent in 

 Polyptems, is probably a primitive structure inherited from a 



common ancestor. A more 

 detailed study of the fossil 

 genera would throw light on 

 this question, which is of con- 

 siderable importance in class- 

 ification (Gegenbaur [153], 

 Boulenger [42]). 



The essential features of 

 the dermal pectoral girdle 

 have been described above 

 (p. 214). It becomes much 

 modified in the higher Actino- 

 pterygii. 



The two halyes of the 

 originally cartilaginous pelvic 

 girdle ossify, except in the 

 Chondrostei, in the form of 

 two horizontal bones lying 

 in the abdominal wall, meet- 

 ing ventrally in front, and 

 bearing the fin -skeleton at 

 their hinder end (Figs. 244- 



Ventral view of the pelvic girdle and fins of Amia 2 4 8). The dorsal iliac pl'OCCSS 



calva, Bon. The skeleton of the right fin is coin- i -p . 11 



pletely exposed, dr, web of left fin with lepido- J S Scarcely if at all TCpre- 



trichia; p, pelvic bone; pr.r, preaxial radial, or epnfprl Small parfilflcrpss mav 



remains of axis. (Partly from Davidoff, from Qwtrt. S '" .' ^ mau Cartilages may 



joum. Micr. Sd.) remain at the anterior ends 



of the bones, and rarely the 



two halves of the girdle may fuse to a small median cartilage 

 (Gadus, Fig. 247). 



On very insufficient evidence it has been argued that the 

 occasional small anterior cartilages represent the true girdle, and 

 that the large pelvic bones are the modified basipterygia of the fins 

 (Davidoff [97-9], Gegenbaur [163], Wiedersheim [491-2]). While 

 Wiedersheim considered these cartilages to represent the first rudi- 

 ments of a developing girdle, Gegenbaur, on the contrary, looked 

 upon them as its last vestiges. Since, however, the pelvic bones 

 are found normally developed in Teleostomes from the Devonian 

 to the present epoch (Eusthenopteron, Fig. 244, Goodrich [173]), there 



FIO. 245. 



