XENOMYSTUS. 



81 



seriated ridge, parallel with the lower border. Gill-membranes extending without a 

 notch across the isthmus. Gill-rakers very short, tubercular, 9 to 11 on lower part of 

 anterior arch. Anal fin with 108 to 130 rays, including the caudal, the longest 

 measuring about three-fourths the length of the head. Pectoral fin as long as the 

 head or a little shorter. Ventral serrature formed of 26 to 30 rather strong spines. 

 120 to 142 scales in the lateral line. 



This fish is uniform brownish in spirit. Sketches made by the late P. Delhez in 

 the Congo represent it as dark purple or purplish brown, the anal olive-grey, the iris 

 dark bronzy green, the pupil sometimes orange. 



200 millim. seems to be the maximum length reached by this species, which is 

 therefore much smaller than its African relative Notopterus afer. 



Measurements (in millimetres) and numbers of fin-rays and scales. 



Total length (without caudal) 



Greatest depth of body 



Length of head 



"Width of head 



Length of snout 



Diameter of eye 



Interocular width 



Length of pectoral fin 



Number of rays in anal fin (including caudal) . . . = 

 ,, scales in lateral line 



1. 



2. 



3. 



4. 



5. 



6. 



7. 



195 



190 



180 



155 



150 



120 



95 



41 



38 



37 



31 



35 



24 



19 



27 



25 



24 



20 



23 



18 



14 



13 



12 



12 



10 



10 



8 



6 



6 



5 



5 



4 



5 



4 



3 



8 



8 



7 



6 



H 



6 



4 



8 



7 



7 



6 



7 



H 



4 



23 



23 



23 



20 



20 



15 



13 



116 



123 



122 



130 



114 



115 



117 



137 



135 



132 



139 



127 



126 



125 



1. Monsembe, Congo. — "Weeks. 



2. Bahr-el-Gebel.— Marno. 



3. 4. L. Chad.— Gosling. 



5. Niger. — Fraser. (Type.) 



6. Bangala Country, Congo. — De Meuse. 



7. Gondokoro. — "Werner. 



First described from the Niger, Xenomystus nigri has since been found in Liberia, 

 in the Gaboon, in the Congo, in the White Nile, and in Lake Chad. The specimens 

 described by Steindachner as X nili were obtained in the Bahr-el-Zeraf and the 

 Bahr-el-Gebel by the Austrian traveller Marno. Dr. F. Werner found further 

 specimens at Gondokoro. 



M 



