22 



PISCES. 



brought together by growth -pressure from before and behind, 

 and exhibiting irregular transverse articulations as the result. 

 The same kind of crowding of the endoskeletal supports is 



FIG. 19. 



Holoptychius (Glyptolepis) leptopterus ; basal cartilages of posterior dorsal fin, 

 with some fin-rays overlapping distally, nat. size. L. Old Bed Sandstone ; 

 N. Scotland. (From Brit. Mus. Catal.) 



FIG. 20. 



Scaumenacia curta ; basal cartilages of anal fin, nat. size. U. Devonian 

 Scaumenac Bay, Canada, a, axonost; b, baseosts; /, bases of fin-rays. 



observed in the posterior dorsal fin of the Crossopterygian 

 Holoptychius (fig. 19), where the basal portions (axonosts) of 



no 



