102 THE ZOOLOGIST. 
searcely be said to be a ground-feeder, but appears to be 
intermediate between the true Carps and the grovelling Loaches. 
The anterior portion of its air-bladder, or what may be termed 
its acoustic part, is more or less enclosed in a bony capsule, 
formed by the parapophyses of some of the anterior cervical 
vertebre. Among the true ground-feeding classes, as Nemacheilus 
and Cobitis, it almost appears as if the posterior two-thirds of the 
air-bladder, or that used for hydrostatic purposes, were deficient, 
this organ being in the form of two rounded lobes placed side by 
side, below the bodies of some of the anterior cervical vertebre 
and where they are enclosed in bone, as observed existed in the 
anterior part of the air-bladder in the genus Botia. It is very 
remarkable that in the elevated regions of Western Turkestan 
the air-bladder of the Loach, Nemacheilus, has become modified, 
for there it exists as seen in Botia, for which reason Kessler has 
formed a new genus, Diplophysa, for their reception. 
Another fresh-water family of Physostomi, the Characinide, 
residents of Tropical Africa and America, are exceedingly inte- 
resting as regards how this organ is modified in respect to hearing, 
a chain of auditory ossicles extending from it to the internal ear, 
as existing in Cyprinide ; while, as already observed, one genus, 
Erythrinus, seems to connect the Physostomi with the Ganoids. 
The extensive fresh-water Physostomatous family of Siluride, or 
sheat-fishes, has likewise some marine representations, and is more 
especially found in tropical countries. Among them the air- 
bladder is remarkably modified, in the majority of instances being 
apparently more useful for auditory than hydrostatic functions, 
and as a general rule smaller in fresh-water than in marine 
species. ‘These fishes are evidently closely allied to the 
Cyprinidae, and in one respect the air-bladder shows a somewhat 
similar modification in the two families. IJ have observed how, 
in the grovelling Loach and some allied forms, it is more or less 
enclosed in a bony capsule, and this is seen both in European 
and Asiatic forms, all of which, however, may be said to be 
ground-feeders. ‘The Siluroids in India likewise live the life of 
eround-feeders, and the power of employing the air-vessel as a 
float appears to be subservient to that of hearing. In the marine 
forms it has thickened walls, and is attached to the bodies and 
processes of some of the anterior vertebree. As we pass inland, 
however, or towards mountainous regions, this organ becomes more 
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