Families of Teleostean Fishes. 163 



Mouth small, toothless ; vertebrae with strong 



parapophyses ; head and body covered with 



spiny scales 20. Gonorhynchidce. 



Mouth small, toothless; no sympleetic ; head 



and body naked 21. Cromeriidce. 



Suborder II. OSTARIOPHTSI. 



Air-bladder, if well developed, communicating with the 

 digestive tract by a duct. Pectoral arch suspended from the 

 skull ; mesocoracoid arch present. Fins without spines, or 

 dorsal and pectoral with a single spine formed by the co-ossifi- 

 cation of the segments of an articulated ray. The anterior 

 four vertebras strongly modified, often co-ossified and bearing 

 a chain of small bones (Weberian ossicles) connecting the 

 air-bladder with the ear. 



This is one of the most natural groups of the class Pisces, 

 although its members are so diversified in outward appear- 

 ance as to have been widely separated in the systems of 

 older authors. It is to Sagemehl* that is due the credit of 

 having first grouped, under the above name, the Characines, 

 the Carps, the Catfishes, and the Gymnotids, the relations of 

 which had been realized to a certain extent by Cope. But it 

 was not until the homology throughout the group of the 

 ossicula auditus, first described by E. H. Weber in 1820, had 

 been demonstrated by Sagemehl that the justification for the 

 course here followed appeared in its full strength, as such an 

 agreement in the structure of so complicated and specialized 

 an apparatus can only be the result of a community of descent 

 of the families which are possessed of it. It is invariably 

 the anterior four vertebra? that take part in the support of the 

 Weberian apparatus. The first vertebra is much reduced; 

 its upper arch is absent and replaced by the ossicles termed 

 claustrum and scaphiiunf, the former being perhaps nothing 

 but the modified neural arch, which fill in the space between 

 the exoccipital and the neural arch of the second vertebra; 

 the principal piece of the apparatus, the tripus, variable in 

 iorm, is related to the third vertebra, of which it is regarded 

 as a modified rib ; a fibrous ligament extends from the ante- 

 rior extremity or the tripus to the scaphium, and in this 

 ligament is inserted the fourth piece, the inter calarium. The 

 various forms of this suborder also show a complete agree- 

 ment in the spinal nerves which pass through these ossicles. 



* Morphol. Jalnb. x. "1885, p. 22. 



f For the nomenclature nf these ossicles, cf. Bridge and Haddon, Proc. 

 Roy. Soc. xlvi. 1889, p. 310. 



