22 Mr. C. T. Regan on the 



usually compressed, often cuspidate ; palate toothless- 

 Hyomandibular with a single head fitting into a groove ; 

 pterygoid normally attached to quadrate. Orbitosphenoid 

 forming a long sutural union with frontals. Dorsal fin 

 median, often rather elongate ; scales usually ciliated ; lateral 

 line, wlien present, straight. 



This very natural group of African fishes corresponds to 

 the Ichthyoborinse, Distichodontince, and Citliarininae of 

 Boulenger, after excluding from the latter the American 

 genera Curimatus and Prochilodus. 



In the following arrangement of the genera important 

 differences in the structure of the lower jaw are for the first 

 time taken into account : — 



I. Rami of lower jaw widely separated for the greater part of their 



length, anteriorly slender and curved together, niovably connected 

 at the symphysis ; dentaiy and articulare firmly united *. 



Scales strongly ciliated ; maxillary rather 

 large, movably articulated withprsmax- 

 illary ; upper jaw not or scarcely pro- 

 jecting beyond the lower; teeth small, 

 bicuspid, in 2 or 3 series. {Xenochara- 



cince.) Nannathiops, Ntolthias, 



Xenocharax. 



Scales strongly ciliated ; maxillary united 

 with prajmaxillary ; upper jaw strongly 

 projecting, toothless anteriorly ; teeth 

 very small, bicuspid, uniserial. {Hemt- 

 stichodunthice.) Hefnistichodu^. 



Scales cycloid, or with the marginal teeth 

 few and strong ; maxillary small, adhe- 

 rent to prajmasillary ; teeth minute, 

 pointed or truncate, uniserial, on the 

 labial margin. (Cithaiinijice.) Citharidium, Citharinus. 



II. Dentaries more or less massive, firmly connected at the symphysis, 



movably articulated with the articulares. 



A. Mouth small, subterminal or inferior ; lower jaw short, with the 

 rather massive dentaries merely coalescent; maxillary well 

 developed, adherent to prtemaxillary ; teeth small, bicuspid, in 

 1 or 2 series. (Diitichodontince.) . . Distichodus,^annochnrax. 



\l. Mouth terminal, rather large, the jaws produced ; dentaries verv 

 n assive, united b\- a long suture ; pr;emaxillaries similar to the 

 dentaries, with the reduced maxillaries united to them by suture. 

 ( Ichth}ioborin(e. ) 



No canines ; teeth biserial, the outer strong, 

 compressed, bi- or tricuspid ; maxillarv 



entering the gape " Euynathkhthys, Para- 



phago, Phago. 



* I find a well-developed angulare in Citharinus, as in other Characi- 

 formes. 



