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In the same family, or that of carps, we find a curious form 
of loach, Botia, in the East Indies, that can scarcely be said to be 
entirely aground feeder, but seems intermediate in habits between 
the true carp and the grovelling loaches. It has the anterior 
portion of its air-bladder, or what may be termed the acoustic 
part, more or less enclosed in bone, this being formed from 
the parapophyses of some of the anterior cervical vertebre. 
All fish with the air-vessel enclosed in bone are bottom 
feeders, and very few are destitute of barbels. In the true 
ground feeding loaches, as the Nemacheilus and Cobitis, it 
almost appears as if the posterior two-thirds of the air-bladder, 
in its hydrostatic portion, were deficient ; the organ being in the 
form of two rounded lobes, placed side by side, below the bodies 
of some of the anterior cervical vertebre, where they are 
almost entirely enclosed in bone. The pneumatic tube, how- 
ever, is still found to exist. In another exclusively ground 
feeding form of carp, Homalopterina, in the East Indies, and in 
which the lower surface of its body appears flat, and its general 
conformation refers to its habit of clinging close to stones at 
the bottom of streams, we find the air-bladder entirely wanting. 
Another fresh-water family of Physostomi, the Characinide, 
residents of tropical Africa and America, are exceedingly 
interesting, as regards how this organ is modified in respect to 
hearing ; a chain of auditory ossicles extending from it to the 
internal ear, as observed in the Cyprinide. While in Erythrinus 
we perceive a most interesting link between the Physostomous 
Teleosteans on one hand and the air-breathing Ganoids on the 
other, for in this genus although the air-bladder is above the 
alimentary canal,the pneumatic tube pierces the left side of the 
throat. The air-bladder is likewise sub-divided by fibrous parti- 
tions, but whether such are exceedingly vascular or not, whether 
this organ is used for respiration or simply for flotation, there 
does not appear at present to be evidence upon which to decide. 
The extensive fresh-water Physostomous family (which has 
likewise some marine representatives) of Silwride, or sheat 
fishes, is very abundant in the tropics. Among them the 
air-bladder is remarkably modified, in the majority of instances 
