THE ORDERS OF TELEOSTOMOUS FISHES 473 



each of which results from the coossification of the segments of 

 a single articulated ray. 



Four suborders are here recognized: (i) Heterognathi Gill 

 (Characins) , (2) Glanencheli Cope (Gymnonoti Gill, Gymnotids) , 

 (3) Eventognathi Gill (Carps), (4) Nematognathi Gill (Catfishes). 

 These exhibit many divergences of form and structure, upon 

 which several orders have hitherto been based. On the other 

 hand, their common origin seems so well assured that Smith 

 Woodward and Boulenger, in adopting Sagemehl's group 

 " Ostariophyseae, " unite them into a single order, without major 

 divisions ; but it here seems preferable to recognize the suborders 

 named above. 



The Characins are undoubtedly the most generalized and are 

 regarded by Boulenger as representing the ancestral stock, which 

 gave off (1) the Gymnotids as a specialized eel-like side branch, 

 and (2) an undiscovered annectant form leading to both Catfishes 

 and Carps. The group is almost exclusively non-marine. 



Order Ostariophysi(«m£'<i). 



Suborder Heterognathi 1 Gill 



The Characins. 



The subordinal characters of this group, as compared with 

 those of the Carps and Catfishes, are nearly all primitive. Thus 

 barbels are lacking, the head is naked, the body covered with 

 cycloid scales, both premaxillaries and maxillaries form the 

 margin of the upper jaw, 2 the premaxillaries are not protrusile, 

 the jaws usually toothed; the upper pharyngeal bones are often as 

 many as four; lower pharyngeals are normal, armed with small, 

 sometimes villiform teeth; the osseous brain-case is not produced 

 between the orbits, an adipose dorsal is often present, the air 

 bladder is transversely divided into two portions ; and (in contrast 

 with the Catfishes) the maxillaries are well developed, the fin 



» 'irspoi, different, yvdQoS, jaw, in allusion to the various modifica- 

 tions of the jaws and teeth. 



2 Save in Ichthyoborus and Neoborus, which parallel the Nematognathi 

 in the reduction of the maxillary and its exclusion from the oral gape 

 (Boulenger). 



