12 POLYPTEBIDA 



compressed. Head once and three-fifths to twice as long as broad, with lateral eyes 

 and convex interorbital region ; snout projecting slightly beyond the lower jaw ; length 

 of snout four to six times in the length of the head ; eye five (young) to eight times in 

 the length of head, once and a half (young) to twice and one-third in the interocular 

 width ; the latter more than the distance between the eye and the spiracle ; cleft of the 

 mouth not extending much beyond the anterior third of the head ; nasal bones in 

 contact on the median line in the adult ; a series of two or three (rarely four) shields 

 between the postorbital and the spiracular shields ; suboperculum as large as or smaller 

 than the eye. Gular plates twice to twice and a half as long as broad. Dorsal fin 

 with 8 to 11 spines, followed by 16 to 19 articulated dorsal and caudal rays; anterior 

 spines more or less widely separated from each other when folded, two and a half 

 to four times as long as broad ; the first spine corresponding to the sixteenth to 

 twenty-first transverse series of scales. Anal fin with 14 to 17 rays. Pectoral fin 

 with 35 to 40 rays, not reaching the vertical of the first spine of the dorsal. Scales 

 smooth, in 53 to 61 transverse series, 34 to 40 round the body. 



The very young is conspicuously marked with dark longitudinal bands, but all 

 markings disappear at a very early age, the fish being uniformly grey, greyish olive, 

 or dark green above, white, cream-colour, or yellow beneath ; the fins immaculate, 

 whitish or greyish, the ventrals, anal, and caudal sometimes yellow or tinged with 

 orange ; the inner side of the pectoral peduncle of a purplish flesh-colour in the 

 young, of a dark purple in the adult ; a more or less distinct dark streak, disappearing 

 with age, from the upper lip to below the operculum ; iris pale golden in some 

 specimens, bronzy in others. 



The external gills do not appear ever to persist in specimens longer than 1 05 milli- 

 metres. Two small specimens, measuring 60 and 69 millim. respectively (see fig. 4, 

 p. 4), were obtained by Mr. Loat in the White Nile, at the mouth of Lake No, in the 

 beginning of February 1901. The external gills measure 5 millim.; the scales are 

 imbricate and rhomboidal, striated, except within the central areola. A dark brown 

 band on each side, from the end of the snout, through the eye, to the base of the 

 caudal fin ; another dark band, only a little narrower, below the first along the body, 

 separated from it by a narrow yellowish streak. 



I have examined numerous other very young specimens, from 39 to 105 millim. long, 

 obtained by Dr. Ansorge and by Mr. Budgett in the Niger Delta. In the largest of 

 these specimens, the external gills measure from 5 to 25 millim., the scales are nearly 

 smooth, and mere traces of the dark bands are visible ; the dorsal and caudal fins bear 

 dark spots. A still smaller and truly larval specimen, 32 millim. long, from the 

 Gambia, has been described and figured by Budgett, Tr. Zool. Soc. xvi. 1901, p. 115, 

 pi. xi. ^g. 1 ; his figure is reproduced above, p. 4. 



500 millim. appears to be the maximum length attained by this species. Our largest 

 specimen measures 420 millim. 



