PELVIC GIUDLB AND FIN OF EUSTHKNOPTERON. 319 



cartilages often found in front of basal supports, represent 

 the first origin of the girdle, hfls not met with much favour 

 for many reasons. More especially the obvious objection 

 may be urged against it, that the pelvic girdle is already 

 fully developed in more primitive forms (Elasmobranchs). 

 Gegenbaur (4), whilst adopting the theory of the homology of 

 the basal supports with the metapterygium of the Selachian 

 fin, considers that the small anterior cartilages of the Ganoids 

 represent the last vestiges of the pelvic girdle, which has 



Fig. I. — Ventral view of the pelvic girdle and fins of Lepidosteus osseus, 

 L. (Partly from DavidofF.) 



undergone degeneration, and may have entirely disappeared 

 in other Teleostomes. 



Now Gegenbaur's view seems to be no less open to 

 objection than Wiedersheim's. For if we are to believe that 

 the girdle has disappeared and beea functionally replaced by 

 bones derived from an ingrowth of the already differentiated 

 fin skeleton, we may well ask, what plausible reason can be 

 given for the substitution in the place of the girdle supports 

 of these new structures of very similar shape, and of perhaps 



VOL. 45, PAUT 2. NKW SKRIES. Z 



