HYDEOCYOJST. 



107 



3. HYDEOCYON BREVIS. 

 (Plate XVI. fig. 2.) 



Hydrocyon forskalii, part., Cuvier & Valenciennes, Hist. Poiss. xxii. p. 309 (1849) ; Peters, Reise 



Mossamb. iv. p. 69 (1868). 

 Hydrocyon brevis, Qiinther, Cat. Fish. v. p. 351 (1864), and Petherick's Trav. ii. p. 245, pi. iii. 



fig. A (1869) ; Steindachner, Sitzb. Ak. Wien, lxi. i. 1870, p. 547. 



Depth of body three and one-third to four and a half times in the total length, length 

 of head three and one-third to four and one-fifth times. Head twice to twice and two- 

 thirds as long as broad ; snout two-sevenths to one-third the length of the head ; diameter 

 of the eye four (young) to seven and a half times in the length of the head, interorbital 

 width three to three and three-fourths times; suborbital and opercular bones more or 

 less distinctly striated ; mouth extending to below the nostrils or the anterior border of 

 the eye, maxillary bone to below the centre or the posterior border of the eye ; 4 or 5 large 

 teeth in the upper jaw and 3 or 4 in the lower. Gill-rakers short, 7 to 9 on lower part 

 of anterior arch. Dorsal fin with II 8 rays, equally distant from the eye and from the 

 root of the caudal, or a little nearer the latter ; second simple ray or first branched ray 

 longest, two-thirds to nearly once the length of the head. Adipose dorsal fin small, 

 about twice as distant from the rayed dorsal as from the caudal. Anal fin with III 

 11-13 (exceptionally 15) rays, longest two-fifths to two-thirds the length of the head. 

 Pectoral fin three-fifths to three-fourths the length of the head. Ventral fin a little 

 shorter than the pectoral, below anterior half of dorsal. Caudal fin deeply forked, with 

 long, pointed lobes. Caudal peduncle once and two-fifths to once and two-thirds as long 

 as deep. Scales 47-54 %p, 4 between lateral line and ventral, 3 between lateral line 

 and scaly process at base of ventral. 



Coloration very similar to that of II. forskalii; longitudinal dark streaks or series 

 of spots, which are more or less distinct in adult specimens, usually confined to the 

 region above the lateral line ; a black spot sometimes present on the adipose 



dorsal fin. 



The largest specimen examined measures 480 millimetres. 



I have counted the fin-rays and scales in a hundred specimens. Nine have 11 



branched rays in the anal ? seventy-one have 12, nineteen have 13, one has 15 ; one has 



47 scales in the lateral line, four have 48, eight have 49, fifteen have 50, twenty-nine 



have 51, twenty-seven have 52, twelve have 53, four have 54. 



Hydrocyon hrevis is known from the Nile (where it appears to be much less generally 



distributed than //. forskalii), the Lake Chad Basin, the Senegal, and the Gambia. 



The types on which the species was founded by Giinther are from Khartum. Great 



p2 



