4:U ^Ir. Ct. a. Boulengei- on 



^[r. Degen, the Cichlids especially showing so many modi- 

 fications, apparently derived from some original stock con- 

 sisting of a small number of forms. These modifications are 

 not comparable in importance to those with which the 

 exploration of Lake Tanganyika has made us acquainted, 

 ])ut they tend to show that this lake has a quite peculiar 

 fauna, bearing no special adinity to cither the Nile or the 

 Congo, so far as specific forms arc concerned. 



Mormyridae. 

 PetrocepJi(tlus Deyeni. 



Depth of body 3^ times in total length, length of head 3| 

 times. Snout very short, about /; length of head, rounded, 

 projecting beyond the mouth ; width of mouth \ length of 

 head ; teeth bicuspid, 10 in upper jaw, 22 in lower jaw ; 

 eye longer than snout, 44 times in length of head, once and ^ 

 in interorbital width. Dorsal 19, originating above first ray 

 of anal, its length twice and \ in its distance from head. 

 Anal 27. Pectoral pointed, about § length of head. Caudal 

 peduncle twice and ^ as long as deep, | length of head. 

 41 scales in lateral line, J'.^ in a transverse series on the body, 

 \' between dorsal and anal, 12 round caudal peduncle. 

 Silvery, back dark grey ; fins grey. 



Total length 88 mm!! 



A single specimen from the mouth of the Katonga River. 



Easilv distinguished from its congeners in the short dorsal 

 fin originating above the first ray of the anal. 



Marciisenins nigrlcdns. 



Depth of body 3 to 3^ times in total length, length of head 

 4 to 4^ times. Snout about \ length of head, rounded, pro- 

 jecting beyond the mouth ; mouth below the nostrils, its 

 width 4 times in length of head ; teeth small, bicuspid, 7 in 

 u| ])er jaw, 8 in lower jaw ; eye as long as snout, ^ to ;5 inter- 

 ocular width. Dorsal 15-18, originating above 5th or 6th 

 ray of anal. Anal 24-25. Pectoral pointed, subfalcate, as 

 lonf as or a little shorter than head. Caudal peduncle 

 twice and ^ to twice and f as long as deep, | to ^ 

 length of head. 46 to 53 scales in lateral line, '^^|^ in a 

 transverse series on the body, ^J_^^ between dorsal and anal, 

 16-20 round caudal peduncle. Uniform blackish brown. 



Total length 93 mm. 



