50 Synopsis of the Fresh Water Fishes., 



as that given to the Hypostomus Eobinii, Val. It attains a 

 length of four or five inches. 



Family. 

 Erythkinid^, Valenciennes. 



Sub-family. 

 Erythkinin^, Gill. 



Genus. 

 Macrodon, Mull. 



Body oblong, compressed, covered by large scales ; the dor- 

 sal and abdominal outlines are but slightly convex, and the 

 former is sometimes rectilinear. 



Head large, compressed, with an obtusely rounded muzzle ; 

 there is only one supratemporal between the fifth sub-orbital 

 plate and the cranium. 



Mouth large, with the gape elliptical and wide. The jaws 

 are nearly equal ; the upper formed above by the small and 

 immovable intermaxillaries, and on the sides by the maxillaries, 

 which are articulated to their extremities. 



Teeth on the intermaxillaries, maxillaries, and dentaries, coni- 

 cal, and acute in a single, unequal row ; on each side of the 

 symphisis of the intermaxillaries there is a long tooth, on the 

 outer side of which are smaller ones ; one or two others of large 

 size exist on each branch, flanked on each side by smaller ones, 

 which gradually decrease as they recede from the larger. 

 Dentaries with large canines, whose apices, when the mouth 

 is closed, are sheathed in corresponding fossettes on the bor- 

 ders of the roof of the palate. There is an anterior row of 

 long conical teeth continued without interruption on the 

 median line, the row being completed in front by some which 

 are placed on an arch concentric with the jaw ; on the inner 



