140 VERTEBRATE ZOOLOGY 



The Cat-fishes, Carps and Their Kin (Ostariophysi) . This is one 

 of the most clearly defined of the sub-orders, and one that possesses 

 certain primitive characters that suggest ganoid affinities. The 

 Cat-fishes (Siluridce) are very common fishes of cosmopolitan dis- 

 tribution, distinguished by the presence of spines and barbels about 

 the mouth (Fig. 77). They are as a rule sluggish and mud-loving. 

 Some of the Cat-fishes reach a very large size, growing to be ten feet 



FIG. 77. A siluroid fish, Rita buchanani. b, barbel; d. f.r. 1, first dorsal fin-ray; 

 d.f. 2, adipose fin; pct.f. r. 1, first pectoral fin-ray; pv.f, pelvic fin; y./, ventral fin. 

 (From Parker and Haswell, after Day.) 



long and weighing in the neighborhood of four hundred pounds. The 

 Gymnotidce are the Electric Eels of South America, the best known 

 species being Gymnotus electricus, a large eel-like fish about eight 

 feet in length, and much feared by the natives on account of the sever- 

 ity of shock it is capable of delivering. The Characinidce comprise 

 about five hundred species of African and South American fishes, that 

 on the whole are the most generalized representatives of the sub-order; 

 their most highly specialized feature is their rather elaborate denti- 

 tion, which is associated with their carnivorous habits. The Cyprini- 

 dce (Carps) are also very generalized, so much so that some authori- 

 ties place them at the bottom of the scale of modern teleosts. A 

 number of senescent armored types of Ostariophysi are known, most 

 of which live in unusual habitats. 



The Symbranchii. This small sub-order of eel-like fishes is doubt- 

 less a senescent derivative of either the Ostariophysi or the Apodes. 

 They are without paired fins, have the gill openings united into a 

 single ventral slit, and have no air-bladder. For our purposes no 

 further characterization is necessary. 



The Eels and Their Kin (Apodes). This sub-order comprises a 



