FISHES. 389 



65. ACHIRUS. Destitute of pectoral fins. Pleuronectes 

 achiriis. 



(3). Ventral fins wanting. Apodal. 



a. Gill opening small, and the gill cover concealed by 

 the skin. 



(AA.) With dorsal fins. 



66. MUILENA. In this great natural group the follow- 

 ing subgenera have been indicated : 1. Anguilla (M. an- 

 gmlla). 2. Conger (M. conger). 3. Ophisurus (M. ser- 

 pens). 4. Mursena (M. helena). 5. Sphagebranchus (S. 

 imberbis). 6. Apterichtes (M. caeca). 7. Synbranchus 

 (S. marmoratus). 8. Alabes, Cuv. In these subgenera 

 many important characters, for their methodical distri- 

 bution, present themselves to those who have access to 

 specimens or figures of the different species. In the An- 

 guilla the pectoral fins are large, in the Muraena they 

 are wanting. In some the anal and dorsal fins are oblite- 

 rated. Ip the Anguilla, the gill openings are lateral ; in 

 Sphagebranchus they are jugular, and in Synbranchus and 

 Alabes, they are jugular and united. 



67. LEPTOCEPHALUS. Body compressed like a ribband. 

 L. Morrisii*. 



(BB). No dorsal fin. 



68. GYMNOTCS. Anus placed anteriorly, and the anal 

 fin extending along the greater part of the belly. 1. Gy- 

 mnotus (G. electricus). %. Carapus (G. macrourus). 3. 

 Sternarchus (G. albifrons). 



b. Gill opening and gill-lid apparent, and of the ordi- 

 nary form. Articulated rays of the dorsal fin simple. 



69. OPHIDIUM. Anal, dorsal, and caudal fins united. 



* Wern. Mem. ii. p. 436, tab. xxii, f. 1, 



