PETROCEPHALUS. 33 



times in the total length. Head as long as deep or a little deeper than long, about 

 twice as long as broad; snout very short, one-sixth to one-fifth the length of the head, 

 rounded, projecting beyond the mouth ; mouth situated below the eye, its width one- 

 fifth to two-sevenths the length of the head ; teeth bicuspid, 14 to 22 in the upper 

 jaw, 22 to 30 in the lower; nostrils close together, on a level with or a little above the 

 lower border of the eye ; eye large, longer than the snout, its diameter one-fourth to 

 two-sevenths the length of the head, and two-thirds to five-sixths the interocular width. 

 Dorsal fin with 29 to 33 rays, originating above the third to tenth ray of the anal, its 

 length once and a half to twice in its distance from the head; anterior rays longest, 

 giving the fin a falcate appearance. Anal fin with 31 to 37 rays, equally distant from 

 the base of the ventral and from the base of the caudal; the anterior rays longest, the 

 fin being falcate like the dorsal in females ; in males, the longest rays form a rounded 

 lobe and pass more gradually into the short posterior rays, and the base of the fin is 

 strongly sinuous. Pectoral fin pointed, two-thirds to three-fourths the length of the 

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

 of the latter. Caudal fin scaled at the base, with pointed lobes. Caudal peduncle 

 twice and two-thirds to three times as long as deep, two-thirds to four-fifths the length 

 of the head. 39 to 50 scales in the lateral line, 5M-* in a transverse series on the body, 

 j^i5 i n a transverse series between dorsal and anal, 10 or 12 round the caudal 

 peduncle. 



In spirit, the fish is silvery, with the back brown, and the extremity of the anterior 

 dorsal rays brownish or blackish. In life, according to Mr. Loat's notes, it has a pure 

 silvery-white appearance, with the dorsal surface greyish, ow T ing to vast numbers of 

 minute dark dots. 



The largest specimen examined by me, a female full of spawn, measures 225 millim., 

 whilst no male exceeds 190 millim. 



I have counted the fin-rays in eighty specimens : of dorsal rays, 29 occur ten times, 

 30 nineteen times, 31 twenty-seven times, 32 sixteen times, and 33 eight times; of 

 anal rays 31 and 32 occur once, 33 twelve times, 34 twenty-nine times, 35 twenty-six 

 times, 36 seven times, and 37 four times. 



Petrocephalus bane is known from the Nile proper, the Blue Nile, the White Nile, 

 the Chad basin, and the Niger. I have examined specimens from the following 

 localities : — 



1 Lower Nile.— Riippell, 1833. 



4 Lower Nile.— Petherick, 1861. 



4 Rosetta branch of Nile, downstream side of barrage. — Loat, 28-30.7.99. 

 1 Nile S. of Cairo, bought in Old Cairo fish-bazar. — Loat, 27.3.99. 



38 Wasta.— Loat, 28.8.99. 



5 Beni Souef.— Loat, 20.8.99, 9.9.99. 



