FIG. 49 



Figs. 49-54. Evolution of paired fins. 49-50. Pectoral and ventral fins of Cladose- 

 lache. X 3. 51. Pectoral fin of Acanthodian, Parexus. (After SMITH WOODWARD.) 52. 

 Pectoral fin of Heptanchus. (After GEGENBAUR.) 53. Pectoral fin of Xenacanthus 

 (Plenmca>if/int.) (After A. FR1TSCH.) 54. " Archipterygial " pectoral fin of Ceratodus. 

 (After HOWES.) 



B. Basal. D. Dermal. R. Radial. 



42 



