302 



A CTINOPTER YG1I 



FIG. 276. 



Division 4. 

 ACTINOPTERYGII. 



The paired fins are non-lobate, the radials having been so much 

 reduced that they scarcely project beyond the body-wall, and the 



web of the fin is almost 



Pia Pm " ''* entirely supported by 



the dermotrichia. The 

 same is the case in the 

 median fins. It cannot 

 be said that there is any 

 evidence of a biserial 

 arrangement of the 

 radials in the paired fins 

 of the Actinopterygii, 

 yet it is usually sup- 

 posed that they have 

 been derived from such 

 an archipterygium by 



Ventral view of the cartilaginous skeleton of the pelvic . , c t M 



girdle and fin of Sco.phirhynclius. (After Rautenfeld.) the lOSS OI the post-axil 

 P/n, median, and I'd, dorsal process of girdle; F, nerve- j- i /pt_., u [~i KO 



foramen ; i-9, radials. radials (Gegenbaur [158, 



162], Braus [48]; see 



p. 108). All distinct trace of an axis has disappeared in the pelvic 

 fin of the Holostei, f . 



where the few remain- * t* A* ? 



ing radials articulate 

 directly with the pelvic 

 bone (Figs. 245 - 8). 

 This is also the case 

 with the pectoral fin 

 of the Teleostei (Figs. 

 243,480). Butin^Trcm 

 and Lepidosteus a basal 

 element persists, bear- 

 ing several radials (Fig. 

 241); and here the fin 

 appears to be built on 

 the rhipidostychous 

 plan, with a post-axial 



n-vic VOT-TT- intorootinrr Ventral view of the endoskeleton of the pelvic girdle 



fixiss. vei_y uiMUTBBUUg and fin of Pofyodou /oZiim, Lac. (After Rautenfeld.) Pm, 



and important is the median, and Pel, dorsal process of girdle ; F, FI, and J*" 2 , 



. i-i i nerve-foramina; 1-13, radials. 



skeleton of the paired 



fins in the Chondrostei (David off [98], Wiedersheim [492], 



Eautenfeld [343], Thacher [434], Salensky [380], Mollier [301]). 



FIG. 277. 



