PETBOCEPHALUS. 39 



4. PETROCEPHALUS DEGENI. 



(Plate X. fig. 1.) 



Boulenger, Ann. & Mag. K H. (7) xvii. 1906, p. 434. 



Depth of body three and a half times in the total length, length of head three and 

 three-fourths times. Head as long as deep, twice as long as broad ; snout very short, 

 about one-sixth the length of the head, rounded, projecting beyond the mouth; 

 mouth situated below the eye, its width one-fourth the length of the head; teeth 

 bicuspid, 10 in the upper jaw, 22 in the lower ; nostrils close together, on a level with 

 the lower border of the eye ; eye rather large, longer than the snout, its diameter four 

 and a half times in the length of the head, once and a half in the interorbital width. 

 Dorsal fin with 19 rays, originating above first ray of anal, its length twice and one- 

 third in its distance from the head ; anterior rays longest, the fin pointed in front. 

 Anal fin with 27 rays, equally distant from the base of the ventral and from the base 

 of the caudal ; anterior rays longest. Pectoral fin pointed, about two-thirds the 

 length of the head, twice as long as the ventral, and extending beyond the vertical 

 of the base of the latter. Caudal fin with pointed lobes. Caudal peduncle twice and 

 a half as long as deep, three-fourths the length of the head. 41 scales in the lateral 

 line, 12 in a transverse series on the body? g in a transverse series between dorsal and 



anal, 12 round the caudal peduncle. 



Silvery ; back dark grey ; fins grey. 



A single specimen, 88 millim. long, from the mouth of the Katonga River, north- 

 west of Lake Victoria, Nov. 5, 1905, forms part of the very important collection made 

 by Mr. E. Degen. 



Measurements (in millimetres). 



Total length (without caudal fin) . 83 



Greatest depth of body 24 



Length of head 22 



"Width of head . . . 11 



Length of snout 4 



Diameter of eye 5 



Interorbital width 7 



Width of mouth . 6 



Length of caudal peduncle 17 



Depth of caudal peduncle ,, . 7 



Length of pectoral fin 16 



P. degeni is easily distinguished from its congeners by its short dorsal fin originating 

 above the first ray of the anal. 



