] 1 CHARAC1N1D.E. 



2. ALESTES. 



Myletes, part., Cuvier, Mem. Mus.iv. 1818, p. 444. 



Alestes, part., Miiller & Troschel, Hor. Ichtbyol. i. p. 12 (1846). 



Alestes, Cuvier & Valenciennes, Hist. Poiss. xxii. p. 179 (1849); Giinther, Cat. Fish. v. p. 312 



(1864); Boulenger, Poiss. Bass. Congo, p. 148 (1901). 

 Brycinus, Cuvier & Valenciennes, t. c. p. 157. 

 Brachyalestes, part., Giinther, t. c. p. 314. 



Snout short ; mouth moderately large ; prsemaxillary bones not movable, with two 

 series of strong teeth few in number, the outer compressed and tri- or quinquecuspid, 

 the inner with molar-like, obliquely truncate or excavated crowns, each armed with 

 several pointed tubercles ; mandibular teeth in two series, the outer composed of 

 several pluricuspid teeth, the inner of a pair of conical teeth ; maxillary bone toothless, 

 moderately large. Cheek covered by the large suborbitals; nostrils near the eye, 

 close together, separated by a valvular flap ; gill-membranes free from the isthmus ; 

 4 branchiostegal rays. Body more or less elongate and compressed ; belly rounded. 

 Scales moderate or large, not ciliated ; lateral line nearer the ventral than the dorsal 

 outline ; a scaly process at the base of the ventral fin. Dorsal fin with 9 to 11 rays, 

 above or behind the vertical of the ventrals ; anal fin with 13 to 30 rays; a small 

 adipose dorsal fin. 



The scales vary, not only in size, but in structure according to the species. In 

 A. dentex and A. baremose the exposed surface of the scales, in addition to the fine 

 concentric striation which can only be seen with the aid of a strong magnifier, is 

 dotted over with minute granular asperities, and a few straight or nearly straight 

 canals radiate from the centre ; if reduced to one, as is the case on some of the scales, 

 the canal is central in position; the tubules of the lateral line are short, occupying 

 not more than half the length of the exposed part of the scale, and emit a short branch, 

 usually directed downwards, as in Hydrocyon. In A. macrolepidotus the exposed 

 surface of the scales is rugose, with interrupted, more or less wavy, longitudinal striae, 

 and the canals are numerous, irregular, and, running in different directions, form a 

 network ; the anterior tubules of the lateral line are much branched, tree-like, whilst 

 the rest are straight and simple, without the downward spur seen in A. dentex. The 

 scales of A. nurse are, in a great measure, intermediate between the two preceding- 

 types. The strise are more distinct than in A. dentex and their direction is inter- 

 mediate between the concentric and the longitudinal ; the canals are few and form 

 arborescent ramifications on the posterior part of the scale ; the tubules of the lateral 



