CA T FISHES 



171 



among these forms which compete most actively for 

 survival. 



To conclude the present chapter, several forms of Tele- 

 osts may be briefly discussed as especially characteristic 

 of the group, namely the catfish, Mormyrus, eel, perch, 

 cod, flounder, porcupine-fish, sea-horse. 



The catfish, representing the Sihcroids, has, as already 

 noted, many structural affinities to the sturgeon, and is, 

 perhaps, a direct descendant of some early type of Mesozoic 

 Palaeoniscoid. It is a representative of a large and wide- 

 spread family, usually of river fishes. Its habits are slug- 



Fig. 177. — The bull-head (catfish), Amiurus melas (Raf.), Jord. and Cope- 

 land. X \. (After GooDE in U. S. F. C.) Eastern North America. 



gish and mud-loving. Its trunk is heavy, rounded, and 

 without Teleostean scales ; its broad mouth margin is pro- 

 vided with barbels ; the fin rays of its dorsal and pectoral 

 fins fuse into a stout, serrate, erectile spine. In North 

 American forms armouring derm plates are developed 

 only on the head roof (Fig. 177). Closely akin to these 

 are the Asiatic genera, and the single European species, 

 Silurus glaiiis, the gigantic Wels of the Danube. The 

 Nile is of interest if only for its forms of catfish to 

 parallel the shapes and structures of the recent Teleosts. 



