PISCES. 



357 



vertebrates are supposed to have been derived from this type 

 (the archipterygium). The median fins consist of one or more 

 dorsal portions which vary in extent, a caudal portion, and a 



FIG. 174. 



FIG. 174. 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. 175? How does 

 Gegenbauer consider that this might give rise to the simpler type of 

 Vertebrate legs? 



FIG. 175. 



FIG. 175. Pectoral girdle and fin of a Teleost. br.o., branchial ossicles; c, coracoid; 

 cl., clavicle; f.r., fin rays; p.cl., post clavicle; p.t., 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? 



