NO. I SCAI.es of AFRICAN FISHES — COCKEREI.L 7 



Micralestcs humilis Boulenger. Ja River. S. Cameroon {G. L. Bates). 



Scale about 4 mm. long and 5.33 broad; structure as in the last. Basal 

 radii one to six; apical one to two; polygonal areas present or 

 absent. 

 Micralestes interruptus Boulenger. Stanley Pool. Congo Free State. 



Scale small, only about 3.33 mm. wide; structure as in the others, but 

 basal circuli less dense. Five basal and three apical radii; polygo- 

 nal areas present. 

 None of the Micralestes show any branching of the apical radii. 



PETERSIUS 



The scales of Petersius are quite as in Micralestes, having the same broad 

 form, with few radii, the apical never branching. 



Group A. Scale relatively large, about 6 mm. long and 9 broad ; apical sculp- 

 ture very feeble. 

 Petersius major Boulenger. Nyong River, Cameroon (G. L. Bates.) 



Basal radii four, apical two. 

 Group B. Scale smaller, diameter about 5 mm, or rather less. Apical circuli 



better developed. 

 Petersius occidentalis Giinther. Infoan (Walker). 



Basal radii about four, variable; sides of scale flatter than in the next. 

 Petersius hilgendorfi Boulenger. Kutu, Lake Leopold II (Delhes). 



The scale examined has only four radii, one basal. Its outline is that of 

 a half circle. 

 Petersius caudalis Boulenger. Boma (Delhez). 



Basal radii two or three; small polygonal areas sometimes developed. 

 The smallest of the Petersius scales. 



CITHARININ.^ 



Herbivorous fishes, with the teeth minute or absent. Gill (Proc. U. S. Nat. 

 Mus. 18. p. 207) suggests that this group should perhaps constitute a distinct 

 family, Citharinidge. The scales are subcircular to transversely oval, zoithout 

 basal radii, wherein they differ from the African Hydrocyoninse, excepting 

 Hydrocyon. 



The following table separates the scales of the species studied : 



Scales ctenoid, with large, sharp apical teeth, but these few and far apart, 

 wholly unlike those of Distichodus, etc.; nuclear area nearly central, 

 and with circuli to middle; circuli very strong, only moderately 

 dense; scales about 2.33mm. long and 3.67 broad. . 



. .Ciiharidium ansorgii Boulenger, 

 Lake Oguta, Nigeria (Ansorge). 



Scales cycloid ^ 



I. Apical area with fewer and coarser circuli, abruptly marked off from 



lateral ^ 



Aoical area not, or not very abruptly, marked off from lateral 4 



