1 64 Natural History of the River Trotct. 



female mature at a length of seven or eight 

 inches. 



" Head well proportioned in its shape, and rather 

 small, when compared with the body. Body rather 

 short and compressed. The posterior point of 

 junction of operculum and sub-operculum is nearly 

 midway between the upper end of the gill opening 

 and lower anterior angle of the sub-operculum. 

 Praeoperculum nearly crescent-shaped, with or with- 

 out a very indistinct lower limb ; snout of moderate 

 length, oblong, conical. Maxillary much longer 

 than the snout, broad, and stout ; in male specimens 

 nine inches long, it extends to or nearly to the 

 vertical from the hind margin of the orbit. Teeth of 

 moderate size. The head of the vomer is triangular, 

 small, broader than long. Vomerine teeth in a 

 double series, sometimes disposed in a zigzag line, 

 persistent throughout life. Fins well developed ; 

 the caudal fin of specimens of nine inches in length 

 is truncate, or scarcely emarginate, the middle 

 caudal rays being more than half as long as the 

 outer ones. The hind part of the body is short and 

 rather high. There are about fifteen scales in a 

 transverse series from behind the adipose fin 

 obliquely forwards to the lateral line ; sides with 

 numerous round or X-shaped black markings. The 

 upper surface or sides of the head, the dorsal, 

 adipose, and caudal fins generally with crowded 



