H.ETEEOTIS. 85 



convex above, its upper surface and sides rugose, granulate in the adult, with large 

 sensory pits ; snout short, rounded, three and three-fifths to five times in the length 

 of the head; eye perfectly lateral, its diameter five and a half to eight times in the 

 length of the head and twice to three and one-fourth times in the interorbital width ; 

 mouth with thick lips, straight and transverse in front, obliquely bent on the sides, 

 nearly square when fully open, extending to below the anterior border of the eye or a 

 little beyond ; a very large dermal flap borders the gill-cover. Gill-rakers long and 

 slender, closely set. Dorsal fin with 32 to 37 thick rays, beginning a little further 

 back than the anal, which is very similar and contains 34 to 39 rays ; the longest rays 

 measure two-fifths to one-half the length of the head, and extend beyond the base of 

 the caudal. Pectoral fin obtusely pointed, three-fifths to two-thirds the length of the 

 head. Ventral fin with 6 rays, one-third to two-fifths the length of the head. Caudal 

 fin short, rounded. Caudal peduncle very short. Scales more or less rugose, 32 to 38 

 in the lateral line, | in a transverse series on the body in front of the ventral fin, 

 jj between the origin of the dorsal fin and the anal. Lateral line extending in a 

 straight line from above the gill-cover to the middle of the caudal peduncle; the 

 canals tubular in the young, deep grooves in the adult. 



According to Ruppell, the fish is reddish brown above, flesh-coloured beneath, the 

 fins brownish red, the iris orange. Kifaud represents the head and sides as olive- 

 green, the back olive-brown, the lips and lower parts pale brown. A sketch made by 

 Delhez on the Senegal represents the fish as pale brown above, yellowish tinged with 

 red on the sides, pinkish white beneath, the sensory pits bluish grey ; fins brownish 

 grey ; mouth, sides of head, and iris golden yellow. And, finally, Mr. Zaphiro has 

 noted the colour of a specimen from Lake Rudolf as greyish, tinged with amber, the 

 fins greyish, the iris white. In the young, the dorsal and anal fins may be marked 

 with rather indistinct darker longitudinal streaks, and each of the scales of the caudal 

 region of the body may bear a round dark spot. 



The largest specimen in the British Museum measures 800 millimetres. 



Heterotis niloticus is known from the Upper Nile, the White Nile, Lake Rudolf, 

 Lake Chad, the Senegal, the Gambia, and the Niger. According to Steindachner, it 

 is not rare in brackish water at the mouth of the Senegal. 



List of specimens examined : — 



1 Nile. 



2 El Kirbekan, near Korti, in pond left by receding Nile.— Loat, 39.5.00 

 1 Omdurman.— Loat, 20.12.00. 



1 Khartum. — Petherick, 1862. 

 8 Fasboda.— Loat, 18-19.1.01. 



3 White Nile, lat. 9°.— Petherick, 1862. 



1 Gabt-el-Megahid, between Sobat and Bahr-el-Zeraf.—Capt. Flower, 15.4.00. 



