576 ON A COLLECTION OF FISHES FEOM LAKE TANGANYIKA. 



Closely allied to M. congicus Blgr. ; distinguished by the fin-formula and the 

 coloration. 



83. Mastacembelus mniatus Blgr. 



Two young specimens, 75 and 38 millim. long, one from Niamkolo Bay (native 

 name Morobi), the other from Kasawa (native name Molombo). 

 The dorsal spines number 33 or 35. 



84. Mastacembelus ophidium Gthr. 



A single specimen, measuring 330 millim., from Burton Gulf. Native name: 

 Molombo. 



Length of head 8| times in total length. 33 dorsal spines. Pale olive-brown 

 above, with roundish spots of a dark brown ; white beneath ; dorsal and pectorals 

 spotted with brown ; anal and caudal of a light orange colour, unspotted. 



We are now acquainted with 7 species of Mastacembelus from Lake Tanganyika. 

 They may be distinguished as follows : — 



I. Vent equally distant from end of snout and from root of caudal fin. 



A. No pi'Eeopercular spine. 



Dorsal XVIII 85 ; Anal II 90 M.frenatus Blgr. 



Dorsal XXV-XXVII 70-80; Anal II 70-80 M. moorii Blgr. 



B. Two prseopercular spines. 



Dorsal XXIX 95-105; Anal II 115-125 M. cmningtoni Blgx. 



II. Vent nearer caudal fin than end of snout. 



A. One or two prseopercular spines. 



Dorsal XXXI 70; Anal II 70 M. ellipsifer Blgr 



Dorsal XXXVI-XXXIX 50-60; Anal II 50-60 M . twngwnMm Gthr. 



B. No prseopercular spine. 



Dorsal XXXIII-XXXV 85; Anal II 85 M . taniatus Blgr. 



III. Vent nearer end of snout than caudal. 



Dorsal XXX-XXXIII 100-120; Aual I 115-130 M . ophidium, Gthr. 



