PISCES 



361 



vertebrates are supposed to have been derived from this type 

 the archipterygium) . 



Pig. 177. 



Fig. 177. Diagram of the anterior fin {archipterygium) of Ceratodus. 



Questions on the figure. — What are the chief points of contrast between this 

 fin and that of Teleosts, figured in Fig. 178? How does Gegenbauer consider that 

 this might give rise to the simpler type of Vertebrate legs? 



Fig. 178. 



Fig. 178. Pectoral girdle and fin oi a Teleost. br.o., branchial ossicles; c, coracoid; c/., 

 clavicle; /.r., fin rays; p.cl.f post clavicle; pA., post temporal which unites with skull; sc, 

 scapula; s.cl., supra-clavicle. By Folsom. 



Questions on the figure. — Which girdle is this, right or left? Do authors 

 regard any of these bones as homologous with similarly named bones in the higher 

 Vertebrates? 



The median fins consist of one or more dorsal portions which 

 vary in extent, a caudal portion, and a ventral part near the 



