HETEEOBRANCHUS . 301 



six-sevenths the length of the head, extending to the extremity of the pectoral fin or 

 between this point and the root of the ventral fin ; outer mandibular barbel once and 

 one-tenth to once and a half as long as inner, which measures once to once and a half 

 the length of the head. Gill-rakers rather short, 20 to 30 on anterior arch. Dorsal 

 fin with 38 to 45 rays, its distance from the occipital process one-tenth to one-sixth the 

 length of the head ; adipose dorsal two-fifths to two-thirds as long as, as deep as, or 

 lower than, and commencing immediately behind the rayed dorsal, extending to the 

 base of the caudal fin. Anal fin with 50 to 57 rays, extending to the base of the 

 caudal fin. Pectoral fin two-fifths to one-half the length of the head, the spine smooth 

 and measuring two-thirds to three-fourths the length of the fin. Ventral fin shorter, 

 midway between the end of the snout and the base of the caudal fin, or a little nearer 

 the latter. Caudal fin rounded, two-fifths to one-half the length of the head. 



The coloration in spirit is a dark olive above and whitish beneath. Mr. Loat 

 descibes the specimen from Goz Shebesha, which is figured on Plate LVL, as dark 

 greenish on the back, shading to paler on the sides, whitish on the belly; the fins 

 dull greyish, with a dull orange-red edge to the dorsal, adipose, and caudal fins. A 

 coloured sketch made by the late P. Delhez at Kaedi, on the Senegal, represents 

 the fish as purplish brown above, yellowish tinged with orange on the sides ; dorsal 

 fins purplish grey, edged with red ; pectoral, ventral, anal, and caudal fins bright red. 



This species grows to a length of four feet. A large specimen seen at Goz abu 

 Guma by Mr. Loat, but of which only a part of the head could be preserved, measured 

 1220 millimetres. The largest specimen brought home by him measures 770 

 millimetres. 



Heterobranchus bidorsalis inhabits the Upper Nile, the White Nile, the Chad Basin, 

 the Senegal, and the Niger. It is a rare fish in the Nile, only four specimens having 

 been brought home by Mr. Loat, although he saw some other very large specimens at 

 Goz abu Guma, on the White Nile. He observes that the fish will take a baited 

 hook, but makes a very poor fight for liberty. The stomach of specimens examined 

 by him contained remains of Synodontis and large mussels. 



I have examined the following specimens : — 



3 Khartum. — Petherick, 1861-3. (Types of II. intermedins.) 



1 Goz Shebesha, White Nile.— Loat, 3.1.01. 



1 Goz abu Guma, White Nile.— Loat, 1.5.01. 



2 Fashoda, White Nile.— Loat, 19-23.3.01. 



1 R. Shari-wasu at Maidugari — Capt. Gosling, 1904. 



3 Kaedi, Senegal.— Delhez, 1899. 



2 Niger.— W. A. Forbes, 1883. 



The specimen figured by Geoffroy, the type of the species, has unfortunately not 

 been preserved, and there is no example to match it in the Paris Museum. It must be 

 noticed that no specimen has ever been found since with the barbels so short as they 



