NO. I SCALES OF AFRICAN FISHES — COCKEREEL 



DISTICHODONTIN^ 



Herbivorous (or partly herbivorous) fishes with ctenoid scales, which re- 

 semble those of the Ichthyoborini. The fact that Bugnathichthys and Ichthyo- 

 borus have quite similar scales, and the absence of any characteristic difference 

 between the scales of the Ichthyoborine and Distichodontine fishes, show that 

 after the development of this type of squamation differentiation took other 

 directions ; hence the scales fail to afford any adequate clue to the minor sub- 

 divisions of these groups. 



In some Distichodus (notospilus, sexfasciatus, air ov entrails, engycephalus) 

 the subapical (exposed) part of the scale is more or less grooved or sub- 

 reticulate, but otherwise there are no substantial differences between the 

 genera and species examined, which are as follows : 



Nannocharax fasciatus Giinther. Kribi River, Cameroon (Bates). 

 Nannocharax niloticus Joannis. River Nile. 



The Nannocharax scales are the smallest of the series, less than 2 mm. 

 broad. This accords with the small size of the fishes. 

 Neolebias unifasciatus Steindachner. Ja River, Cameroon (Bates). 



Scales about 2.33 mm. broad. 

 NanncBthiops imitceniatus Giinther. Sette Cama, Gaboon (Gerrard). 



Scales about 4 mm. broad; basal plication very strong. The scales are 

 longer in proportion to their breadth than those of Neolebias. 

 Xenocharax spilurus Giinther. Ibali, Lake Leopold II (Delhez). 



Scales about 4.25 mm. long and 5 broad. 

 Distichodus antonii Schilthuis. Monsembe, Upper Congo (Weeks). 



In tEis species and D. atroventralis the scale is unusually broad in pro- 

 portion to its length. 

 Distichodus atroventralis Boulenger. Kutu, Lake Leopold II (Delhez). 



I do not know how to distinguish the scale definitely from that of D. 

 antonii. 

 Distichodus engycephalus Giinther. River Nile at Cairo (Loat). 



Scales not quite 5 mm. long, about 6 broad; apical (exposed) area 

 reticulate. 

 Distichodus fasciolatiis Boulenger. Monsembe, Upper Congo (Weeks). 



Scales about 3 mm. broad ; nuclear area more or less rugose. 

 Distichodus brevipinnis Gunther. Fashoda, White Nile (Loat). 



Scales little broader than long, shaped as in D. niloticus, but larger. 

 Distichodus niloticus Linnaeus. Fashoda, White Nile (Loaf). 

 Distichodus rostratus Giinther. Gondokoro, White Nile (Loat). 



Scales quite as in D. niloticus; dermal pigment-spots also the same. 

 Distichodus lusosso Schilthuis. Banzyville, Ubangi (Capt. Royaux). 



Scales small, less than 3 mm. diameter; subapical field broadly rugulose. 

 Distichodus mossambicus Peters. Loangwa River, N. W. Rhodesia (S. A. 

 Neave) . 

 Nuclear area very broadly rugulose; a subdorsal scale is broader in pro- 

 portion to its length than one from near the lateral line. 

 Distichodus sexfasciatus Boulenger. Coquilhatville, Upper Congo (Delhez). 

 Scale rather broad ; apical field with radiating grooves. 



