The Class Elasmobranchii or Shark-like Fishes 519 



the Notidani and Cestraciontes, culminating in the Lamnoid 

 and Galeoid sharks. 



Still another series, destitute of anal fin, probably arising 

 near the Acanthodei, reaches its highest development in the 

 side branch of the Batoidei or rays. The Holocephali and 

 Dipneusti must also find their origin in some of these primitive 



FIG. 306. Pleuracanthus decheni Goldfuss. Family Pleuracanthidce. 

 (After Roemer, per Zittel.) 



types, certainly not in any form of more highly specialized 

 sharks. 



Woodward prefers to place the Tectospondyli next to the 

 Ichthyotomi, leaving the specialized sharks to be treated later. 

 There is, however, no linear system which can interpret natural 

 affinities, and we follow custom in placing the dogfishes and 

 rays at the end of the shark series. 



