402 ME. G. A. BOULENGEE ON A COLLECTION OE FISHES 



wliere it is connected with the Botletle. The explanation of this change in the water- 

 supply of the lake is to be found in the fact that previously one of the many large 

 channels of the Okovango, called the Teoughe, ran into the lake at the north-west 

 corner, but by a natural process of reed-growth and silting-up this channel has 

 gradually become choked, till now no water at all finds its way into the lake from the 

 north-west, and its only source of supply is at the south-east corner, where it is 

 connected with the Botletle by a kind of backwater or arm, and through this it 

 receives a certain amount of water when the floods have risen sufficiently high in 

 the Botletle*. Into this backwater from the Botletle another channel from the 

 Tamalakan (merely another name for the upper part of the Botletle) also runs, which 

 brings a good deal of water towards the end of the flood season, but the lake never 

 fills now to anything like its former level. 



" As far as the value of the fish collection goes, I feel quite confident that there are 

 not and never have been any fish in Lake Ngami which are not also in the Okovango 

 and marshes, and although it would have been of interest geographically to penetrate 

 to the centre of the lake, it would not have produced many new fish. But that there 

 are fish in the upper waters of the Okovango which are not found in the marshes is 

 highly probable." 



M OEM YRID^. 



1. Maecusenius CASTELNAur, sp. n. (Plate XXXVIII. fig. 1.) 



Depth of body 3 times in total length, length of head 3f times. Head as long as 

 deep, twice as long as broad ; snout rounded, j length of head, projecting very slightly 

 beyond mouth ; mouth small, well below level of lower border of eye ; teeth small, 

 notched, 7 in upper jaw, 8 in lower ; eye rather indistinctly defined, nearly as long as 

 snout, its diameter not ^ interocular width; posterior nostril a little lower down than 

 upper, close to eye. Dorsal fin 17, originating above fourth ray of anal, its length 

 half its distance from head, upper border slightly convex in front, longest ray f length 

 of head. Anal 23, similar to dorsal but longer, equally distant from base of ventrals 

 and from base of caudal. Pectoral pointed, a little shorter than head, twice as long 

 as ventral, extending to middle of latter. Caudal fin with rather short, rounded lobes. 

 Caudal peduncle 2^ times as long as deep, a little shorter than head. 48-50 scales 

 in lateral line, j^^ in transverse series on body, f in transverse series between dorsal 

 and anal, 12 round caudal peduncle. Pale brownish, darker on the back, spotted and 

 marbled with dark brown ; fins brown. 



Total length 70 mm. 



* "Livingstone says that 'this channel has never been observed to flow either vray, and is as stagnant as 

 the late itself.' This is certainly not so at the present day, for at the time of our visit it was running into 

 the lake in a strong deep stream." 



