CLASS IV. ORDER T. Si 



SYNBRANCHUS, (surinam-eel,) body eel-form ; 

 pectoral fins none ; spiracle single, beneath the 

 neck. 



SPHAGEBRANCHUS, body eel-form ; pectoral fins 

 none ; spiracles two. beneath the neck. 



MONOPTERUS, body eel-form ; nostrils placed 

 between the eyes ; fin caudal. 



GYMNOTUS, (electrical-eel,") head with lateral 

 opercula ; tentacula two on the upper lip ; eyes 

 covered by the common skin ; gill-membrane 5- 

 rayed ; body compressed and carinated by a fin 

 beneath. In most species no dorsal fin. 



OPHIDIUM, (eel-fish,) head somewhat naked,, 

 teeth in the jaws and palate and throat ; branch!- 

 ostegous membrane 7-rayed, patulous ; body en- 

 siforrn. 



ODONTOGNATHUS, mouth furnished with a strong 

 moveable lamina or process on each side of the 

 upper jaw ; gill- membrane 5-rayed. 



COMEPHORUS, head large, with depressed snout 5 

 mouth large, with small teeth ; body elongated, 

 compressed ; the second dorsal fin furnished with 

 several long naked ra^s. 



TRIURUS, (tripple-tail,) snout cylindric ; tooth 

 single in each jaw ; fin, dorsal and anal, extend- 

 ed beyond the tail. 



AMMODYTES, (launce,) head compressed, nar- 

 rower than the body ; upper lip doubled ; lower 

 jaw narrow, pointed ; teeth small and sharp ; gill- 

 membrane 7-rayed ; body long, roundish, with 

 very small scales ; tail distinct. 



LEPTOCEPHALUS, (morris,) head small, narrow : 

 body very thin, compressed ; pectoral fins none. 



STYLEPHOHUS, (thread-tail,) eyes pedunculated, 

 standing on a short thick cylinder ; snout length- 



