FISHES 345 



The living lungfishes are the Australian Neo- 

 ceratodus or barramunda, the Lepidosiren of 

 South America, and the Protopterus of Africa. 

 (c) Subclass Teleostomi, or true fishes. Some include TheTeieo- 

 the lungfishes with these ; others separate out Jnwteh'es 

 additional subclasses for certain ancient types 

 surviving in few species, including in one the 

 curious African genus Polypterus, in another the 

 sturgeon and the paddlefish. It is difficult to 

 define the Teleostomi, as they are so numerous 

 and diverse, but the skeleton is at least partly 

 bony ; there is only a single gill opening on each 

 side, leading to gill arches on which are gill fila- 

 ments ; and there is a swim bladder, which may 

 disappear with age. In the higher forms, with 

 wholly bony skeleton and stiff fin rays, the pelvic 

 girdle approaches the pectoral one, so that the 

 pelvic fins may be directly below the pectorals. 

 Thus it is possible to arrange the multitudes of 

 fishes in groups representing different degrees of 

 specialization, and it is not necessary to know 

 much about the subject to perceive that a 

 perch stands higher in the series (i.e., is more 

 remote from the common ancestor) than a 

 herring. It is also evident that the land verte- 

 brates (amphibians) could not have arisen from 

 the higher fishes : first because of the position 

 of the fins in the latter, and secondly because 

 the structure corresponding to the lungs in 

 these fishes has been modified into the swim 

 bladder. 



3. Agassiz recognized a large group of fishes, nearly Ganoid 

 all extinct, which he called Ganoids. The name is de- fishes 

 rived from ganos, brightness (Greek), in allusion to the 



