CHAPTER VIII 
SERIES OSTARIOPHYSI 
%)|\STARIOPHYSI.—A large group of orders, certainly of 
common descent, may be brought together under the 
an f| general name of Ostariophysi (écraptov, a small bone; 
6vods, inflated). These are in many ways allied to the Jso- 
spondyli, but they have undergone great changes of structure, 
some of the species being highly specialized, others variously 
degenerate. A chief character is shared by all the species. The 
anterior vertebre are enlarged, interlocked, considerably modi- 
fied, and through them a series of small bones connect the air- 
bladder with the ear. The air-bladder thus becomes apparently 
an organ of hearing through a form of connection which is 
lost in all the: higher fishes. 
In all the members of this group excepting perhaps the degraded 
eel-like forms called Gymnonoti, the mesocoracoid arch persists, 
a trait found in all the living types of Ganoids, as well as in the 
Teleost order of Isospondylt. Other traits of the Ostariophysan 
fishes are shared by the Isospondylt (herring, salmon) and other 
soft-rayed fishes. The air-bladder is large, but not cellular. It 
leads through life by an open duct to the cesophagus. The ven- 
tral fins are abdominal in position. The pectorals are inserted 
low. A mesocoracoid arch is developed on the inner side of 
the shoulder-girdle. (See Fig. 119) There are no spines on 
the fins, except in many cases a single one, a modified soft ray 
at front of dorsal or pectoral. The scales, if present, are cycloid 
or replaced by bony plates. 
Many of the species have an armature much like that of 
the sturgeon, but here the resemblance ends, the bony plates 
in the two cases being without doubt independently evolved. 
According to Cope, the affinities of the catfishes to the sturgeon 
are “seen in the absence of symplectic, the rudimentary maxillary 
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