368 INDIAN CYPRINID&. Peonomine. 
Some of the Gudgeons might from the situation of the mouth be describ- 
ed as Gonorhynchs ; the latter differ from the former chiefly in having the 
lower jaw formed for uprooting a scanty food derived from plants that are 
fixed, rather than for merely collecting such as are loose and floating plenti- 
fully throughout the waters they inhabit. The two groups have therefore the 
nearest affinities to each other, the nature of the food, and the structure of 
the digestive organs being nearly the same in both. The difference between 
them arises rather from the circumstances in which they are respectively 
placed, than from any thing peculiar to the nature of either, that the other does 
not possess ; and may be traced perhaps to an easy existence on the one hand, 
in the still waters of ponds and lakes, amidst abundance of food derived from 
loose, floating vegetation ; and, on the other, to the precarious struggle for 
life in mountain torrents, liable to sudden and violent floods, which as sudden- 
ly subside. These conditions seem to allow of the weak jaws, clumsy bodies, 
and feeble fins of the Gudgeons; and to require in the Gonorhynchs a struc- 
ture more adapted to battle against the difficulties of their situation in the cold 
rocky streams of high altitudes, where aquatic vegetation is scanty, and only 
to be obtained by force from the slippery surface of boulders, and water-worn 
rocks. The most remarkable character which belongs to the group, is a cir- 
cular disk or sucker, which is placed on the lower surface of the head, behind 
the lower jaw. This is no doubt used in cases of difficulty for adhering to 
rocks, and thus resisting the violence of mountain torrents which, without 
such a contrivance they would be unable to withstand. This character, no 
less than the inferior position and structure of the mouth, seems to indicate a 
relation with the Palatycara, Lampreys, and Cyclopterus. Their fins are 
strong, but not large, and the rays are soft, and often enclosed in a thick 
membrane : their bodies are elongated, by which they are rendered more 
manageable in rapid currents, while the peculiar structure of the lower 
jaw affords an instrument singularly adapted for obtaining the only 
food procurable in the rocky basins to which they are confined. These 
