272 
Artificial key tort her oemean. 
I, Maxillary and mandibulary barbels present. 
io Abate Cia PRICE JOKES Gos e¢Anoaos 09 Arius p. 272. 
2. Palate edentulous. 
a. Mouth wide, reaching behind eye. Closely 
set incisor-like teeth in a single series in 
WON EA VGelaaot nee col auc 6. Utomo la cm eae Ketengus p. 317. 
4, Mouth narrow, ending before eye. No incisor- 
like teeth in the jaws. 
«, A narrow patch of conical teeth, few in 
number, on each side of the jaws. 8 short 
gillrakers. Gillmembranes with free poste- 
MOR WEMB 6 5 oD oO OE AO 0-0) OO Tetranesodon p. 318. 
@. 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 
PECSEB boy ee hs peers cones s: fn) Nevnencon oes ee ree ... . Osteogeneiosus p. 329. 
III. Only a pair of small mandibulary barbels developed Latrachocephalus p. 331. 
1. 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 
