2/2 



Artificial key to the genera. 



I. Maxillary and mandibulary barbels present. 



1. Teeth on palate present Arius p. 272. 



2. Palate edentulous. 



a. Mouth wide, reaching behind eye. Closely 

 set incisor-like teeth in a single series in 



the jaws JCetengus p. 317. 



b. Mouth narrow, ending before eye. No incisor- 

 like teeth in the jaws. 



oc. A narrow patch of conical teeth, few in 

 number, on each side of the jaws. 8 short 

 gillrakers. Gillmembranes with free poste- 

 rior margin Tetranesodon p. 318. 



/3. Minute teeth in I or 2 series in the jaws. 

 More than 30 long gillrakers. Gillmem- 

 branes totally confluent with skin of isth- 

 mus, without free posterior margin .... Nedystoma p. 320. 

 y. Bands of villiform teeth in the jaws. Gill- 

 rakers short, few or moderate in number. 



Gillmembranes with free posterior margin. Hemipimelodus p. 322. 

 II. Only a pair of stiff, osseous, maxillary barbels 



present Osteogeneiosus p. 329. 



III. Only a pair of small mandibulary barbels developed Batrachocephalus p. 331. 



I. Arius Cuvier & Valenciennes. 

 (CUVIER & VALENCIENNES, Hist. Nat. Poiss. XV. 1840, p. 53). 



Elongate, posteriorly compressed. Head dorsally with more 

 or less granular or rugose osseous shields. Occipital process 

 touching the basal bone of the dorsal spine. Upper jaw 

 projecting before moderate or large transverse or arcuate 

 mouth, wich has thin lips. Nostrils close together, the posterior 

 with a valve, situated superiorly near the frontborder of the 

 snout. Eyes lateral or slightly directed upward, with a free 

 orbital margin. A pair of maxillary, mandibulary and mental 

 barbels. A short dorsal with 7 rays and a pungent spine, 

 situated between pectorals and ventrals. Adipose fin short or 

 of moderate length, opposite to short anal. Pectorals with a 

 pungent spine. Caudal forked, with rounded or acute lobes. 

 Teeth in the jaws in bands, on the palate villiform, granular 





