V. Nannocharacina.—A short dorsal and an adipose fin; teeth in both jaws well developed; notched incisors. The gill-membranes are grown to the isthmus. Nostrils close together.
One genus, Nannocharax, with two species only, from the Nile and Gaboon; very small.
VI. Tetragonopterina.—A short dorsal and an adipose fin; the teeth in both jaws well developed, compressed, notched, or denticulated; the gill-membranes free from the isthmus, and the nasal openings close together. South America and Tropical Africa.
Alestes.—The dorsal fin is placed in the middle of the length of the body, above or behind the ventrals; anal fin rather long. Body oblong, covered with scales of moderate or large size; belly rounded. Cleft of the mouth rather small. Maxillary teeth none; intermaxillary teeth in two series; those of the front series more or less compressed, more or less distinctly tricuspid; the teeth of the hinder series are broad, molar-like, each armed with several pointed tubercles. Teeth in the lower jaw in two series; those in the front series laterally compressed, broader behind than in front; the hinder series is composed of two conical teeth. All the teeth are strong, few in number.
Fourteen species from Tropical Africa; several inhabit the Nile, of which the “Raches” (A. dentex and A. kotschyi) are the most common.
Tetragonopterus.—The dorsal fin is placed in the middle of the length of the body, above or immediately behind the ventrals; anal fin long. Body oblong or elevated, covered with scales of moderate size; belly rounded. Cleft of the mouth of moderate width. Anterior teeth strong, lateral teeth small. Intermaxillary and mandibulary teeth subequal in size, with a compressed and notched crown, the former in a double, the latter in a single series; maxillary with a few teeth near its articulation, rarely with the entire edge denticulated.
Of all the genera of this family Tetragonopterus is represented by the greatest number of species; about fifty are known. Some of them seem to have a very wide range, whilst others are merely local. All are of small size, rarely exceeding a length of eight inches.
Chirodon.—Dorsal fin placed in the middle of the length of the body, behind the ventrals; anal long or of moderate length. Body oblong, covered with scales of moderate size; lateral line not continued to the tail. Belly rounded before the ventrals. Cleft of the mouth narrow, maxillary short. A single series of small serrated teeth in the intermaxillary and mandibulary; maxillary teeth none.
Fig. 277.—Chirodon alburnus.