CHAPTER VIII 

 SERIES OSTARIOPHYSI 



STARIOPHYSI. A large group of orders, certainly of 

 common descent, may be brought together under the 

 general name of Ostariophysi (ocrrapiov, a small bone; 

 6v<r6s, inflated). These are in many ways allied to the Iso- 

 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 vertebrae 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 Gymnonot-i, the mesocoracoid arch persists, 

 a trait found in all the living types of Ganoids, as well as in the 

 Teleost order of Isospondyli. Other traits of the Ostariophysan 

 fishes are shared by the Isospondyli (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 oesophagus. 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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