136 CHAEACINIDjE. 



the skin very thin and adherent to the bones. Gill-rakers extremely short, rudi 

 mentary. Dorsal fin originating immediately behind the vertical of the base of the 

 ventrals, equally distant from the occiput and from the root of the caudal ; its rays 

 III 12-14 ; the first branched ray longest, two-thirds to three-fourths the length of the 

 head. Adipose fin once and one-third to once and two-thirds as distant from the 

 rayed dorsal as from the caudal. Anal with III 11-14 rays ; anterior branched rays 

 more than twice as long as the posterior, and two-fifths to three-fifths the length 

 of the head. Pectoral fin about half the length of the head, as long as the ventral, 

 from which it is widely separated. Caudal fin nearly entirely covered with very small, 

 thin scales, deeply forked, the lobes rounded or obtusely pointed. Caudal peduncle 

 once and two-thirds to twice as long as deep. Scales 91-112 ^j 6 , 10-12 between 

 the lateral line and the root of the ventral fin. 



Silvery, back pale olive ; an iridescent, greenish golden streak above the lateral 

 line ; some specimens with blackish spots or marblings on the back and sides ; fins 

 whitish, except the caudal, which is pale yellow, with more or less numerous black 

 spots ; iris olive-grey, with a yellow ring round the pupil. 



Total length 190 millimetres. 



This curious fish was discovered in May at Thebes, in the beginning of the last 

 century, by de Joannis, who was informed by the Arabs that the " Besse," as they 

 called it, is extremely rare there, only appearing certain years, and falling into the 

 nets two at a time, from which fact he infers that they descend the Nile in pairs for 

 the purpose of breeding. The description given by de Joannis is not very correct, 

 it seems to me, and I can place no reliance on the number of transverse series of 

 scales as represented in the figure. For this reason I must differ from Dr. Giinther 

 and regard the fish sent from Khartum by Petherick, in 1862, and described as 

 /. microlepis, as identical, the points of agreement with de Joannis's description and 

 figure far outweighing the discrepancies. Only two specimens were found by Petherick. 

 Mr. Loat was fortunate enough in securing as many as sixty-seven specimens at 

 various localities on the White Nile, in the beginning of 1901. These specimens 

 show no signs of approaching the breeding-season, and Mr. Loat was not able to make 

 any notes concerning their habits. 

 List of specimens examined : — 



2 Khartum. — Petherick, 1862. (Types of I. microlepis.) 



3 Between Khartum and Sobat K. — Zaphiro, 1-2,04. 



1 Groz Abu Guinah, White Nile. — Loat, 1.5.01. 



2 20 miles K of Kaka, White Nile.— Loat, 25.4.01. 

 58 Nile at Fashoda.— Loat, 14-28.3.01. 



1 In a kore at Fashoda. — Loat, 29.3.01. 



2 Polkom, Baro R. (Sobat).— Zaphiro, 4.04. 

 2 Mouth of Lake No.— Loat, 25-28.2.01. 



1 Lake No.— Loat, 20.2.0L 



