474 WILLIAM K. GREGORY 



rays all soft, the body scaly, the parietals not fused with the 

 supraoccipitals. 



None of their independent specializations is of subordinal 

 value, but in the typical Characins (i) the skull is "more or less 

 invaded by reentering valleys from behind, " (2) the supraoccipi- 

 tal is "partly superior and carinated by a procurrent crest" 

 (Gill) , (3) the ribs are mostly sessile, all the greater number of the 

 precaudal vertebrae being without parapophyses (Boulenger.) 



The Characins, although clearly allied to the other Ostario- 

 physi, show many analogies in appearance with the Salmonidse 

 among Isospondyles. They present a great range of genera and 

 species characteristic of the fresh waters of tropical America and 

 Africa south of the Sahara. In Africa they accompany their re- 

 mote relatives the Carps, but in tropical America they entirely 

 replace them. Many are extremely predaceous, others are ex- 

 clusively vegetable feeders; the dentition is equally diversified. 1 



A peculiar group, the Gymnotidae, or Characin Eels, was given 

 ordinal rank (Gymnonoti) by Cope, Gill, and others, but Rein- 

 hardt has proved that they are simply a highly specialized 

 offshoot from the Characins, from which they differ chiefly in 

 the eel-like body, obsolete dorsal and pectoral fins, and forward 

 shifting of the anus to a point near the throat. They exhibit 

 close analogies (due to living in turgid rivers) to the eel-like 

 Mormyrs of Africa (Appendix I). The famous Electric Eel 

 (Gymnotus electricus) also parallels the Mormyrid Gymnarchus 

 and the Electric Catfish (Malapterurus) in the possession of an 

 electric organ on either side of the tail. 



Comparison of the Chief Diagnostic Characters of the Suborders 



of Ostariophysi. 

 (Compiled from Jordan and Evermann, Eigenmann, Boulenger.) 



Heterognathi Eventognathi Nematognathi 



(Characins) (Carps) (Catfishes) 



Body Scaly Scaly or naked . . . Naked or armed 



with bony plates . 



Head Naked Naked Naked or armed 



with bony plates. 



Barbels None Present or absent Present. 



Mouth Not protractile . . . More or less pro- Not protractile. 



tractile. 



1 See Eigenmann, C. H., in Biol. Bull., Vol. VIII, Jan, 1905 p. 61. 



