STEENOPTYCHIDiE. 627 



Like Mormyrus, Gymnarchus posseses a pseudo-electric organ, 

 thickest on the tail, taperiag in front, and extending nearly 

 to the head. It consists of four membranaceous tubes inti- 

 mately connected with the surrounding muscles, and con- 

 taining prismatic bodies arranged in the manner of a pater- 

 noster. The air-bladder of Gymnarchus is cellular, very 

 extensible, and communicates with the dorsal side of the 

 oesophagus by a duct possessing a sphincter. 



[See Erdl, Munchner Gelehrte Anzeigeii, 1846, xxiii., and Hyrtl, 

 Denksohi'. Akad. Wiss. Wien. 1856. xii.] 



Thietbenth Family^ — Steknoptychid^. 



Body naked, or ivith very thin deciduous scales; harhels 

 none. Margin of the upper jaw formed hy the majxAllary and 

 intermaxillary, loth of which are toothed ; opercidar apparatus 

 not completely developed. Gill-opening very wide; pseudo- 

 hranchice present or absent ; air-hladder simple, if preseyit. 

 Adipose fin present, hut generally rudimentary. Series of phos- 

 phorescent bodies along the lower parts. The eggs are enclosed 

 in the sacs of the ovarium, and excluded hy oviducts. 



Pelagic and Deep-sea fishes of small size. 



Sternoptyx. — Trunk much elevated and compressed, with 

 the trunk of the tail very short. Body covered with a silvery pig- 

 ment, without regular scales ; series of phosphorescent spots run 

 along the lower side of the head, body, and tail. Cleft of the 

 mouth wide, vertical, with the lower jaw prominent. Jaws 

 armed with small teeth. Eyes rather large, and although lateral, 

 directed upwards and placed close together. Ventral fins very 

 small. A series of imbricate scutes runs along the abdomen, 

 forming a kind of serrature. The dorsal fin is short, and occu- 

 pies about the middle of the length of the fish ; it is preceded by 

 the first commencement of the formation of a spinous dorsal, 

 several neural spines being prolonged beyond the dorsal muscle 

 forming a triangular osseous plate. Adipose fin rudimentary ; 

 anal short ; caudal forked. 



