MOKMYEID^E. 



7. GYMNARCHUS. 



Cuvier, Regne Anim. 2nd ed. ii. p. 357 (1829) ; Giinther, Cat. Fish. vi. p. 225 (1866) ; 

 Boulenger, Proc. Zool. Soc. 1898, p. 821. 



Teeth forming a single complete series on the entire edge of both jaws (14 in the 

 upper, 24-28 in the lower), with compressed, pointed, truncated, or slightly notched 

 crowns finely serrated on the sides ; palate and tongue toothless ; mouth wide, terminal. 

 Nostrils far apart, remote from the eye. Body much elongate, the tail gradually 

 attenuated into a filament. Dorsal fin occupying the whole length of the body ; anal, 

 ventral, and caudal fins absent. Vertebrae 114-120 (45-47 + 67-75). Air-bladder 

 cellular, lung-like. 



A single species. 



1. GYMNARCHUS NILOTICUS. 

 (Plate XIII.) 



Rifaud, Voy. Egypte, pi. 138 bis (1830). 



Gymnarchus niloticus, Cuvier, Regne Anim. 2nd ed. ii. p. 357 (1829) ; Erdl, Abh. Bayer. Ak. v. 



1847, p. 209, pi. v. ; Heckel, Denkschr. Ak. Wien, vi. 1854, p. 11, pi. i. ; Hyrtl, Denkschr. 



Ak. Wien, xii. 1856, p. 1, pis. i.-iv. ; Giinther, Petherick's Trav. ii. p. 257 (1869) ; Stein- 



dachner, Sitzb. Ak. Wien, lxi. i. 1870, p. 556 ; Boulenger, Proc. Zool. Soc. 1898, p. 821 ; 



Budgett, Tr. Zool. Soc. xvi. 1901, p. 126, pi. xi. figs. 4 & 5. 



Depth of body seven to ten and two-thirds times in the total length, length of head 

 five and one-third to six and three-fourths times. Head twice to twice and a half as 

 long as deep, a little more than twice as long as broad ; snout rounded, scarcely 

 projecting beyond the lower jaw ; eye very small ; interorbital width one-seventh 

 (young) to one-fourth the length of the head ; a strong fold of the skin connecting the 

 gill-openings across the isthmus. Dorsal fin with 183 to 200 rays, extending from the 

 nape to near the end of the tail. Pectoral fin rounded, one-third to one-fourth 

 the length of the head. Scales very small, largest along the middle of the side ; the 

 skin of the muscular portion embracing the basal bones of the dorsal fin forming straight 

 or slightly wavy longitudinal folds, between which series of very small scales run. The 

 cylindrical portion of the tail projecting beyond the dorsal fin entirely covered with 

 minute scales or partly naked and of india-rubber-like consistence. Caudal region 

 about one-fourth longer than head and body. 



Specimens in spirit are olive or brown above, whitish beneath, the end of the tail 

 blackish. A fresh specimen sketched by the late P. Delhez on the Senegal was of a 

 beautiful violet-purple on the back, shading to blackish purple behind, the lower parts 



