CHAP. XXI MALACOPTERYGII 557 
glossohyal toothed; mandibular barbels; branchiostegal rays 
15 to 17; body compressed, with trenchant abdomen ; coracoids 
forming a ventral keel; dorsal fin short; ventral fins nearly 
equally distant from end of snout and caudal fin; vertebrae 
29 to 31 +30; air-bladder not cellular. One species from the 
northern parts of Australia, and one from Sumatra. Banka, and 
Borneo. 
Osteoglossum.—Mouth large; vomer, palatines, pterygoids, and 
glossohyal toothed ; mandibular barbels ; branchiostegal rays 10 ; 
body compressed, with trenchant abdomen ; coracoids forming a 
ventral keel; dorsal fin long; ventral fins nearly twice as far 
from the caudal as from the end of the snout; vertebrae 28 + 59 ; 
air-bladder not cellular.—South America (Guianas, Brazil). 
Arapaima.—Mouth rather large; vomer, palatines, ptery- 
goids, and glossohyal toothed; branchiostegal rays 16; belly 
rounded; dorsal. fin rather long; ventral fins equidistant from 
head and caudal fin; vertebrae 36 to 38 +41 to 42; air-bladder 
cellular.—South America (Guianas, Brazil). 
Heterotis—Mouth moderate; branchiostegal rays 7; belly 
rounded ; dorsal fin rather long; ventral fins nearer end of snout 
than caudal fin; vertebrae 27 +42 to 43; air-bladder cellular ; 
fourth branchial arch with an accessory breathing-organ.— Africa 
(Nile, Senegal, Gambia, Niger). 
Dapedoglossus, from the Eocene of Wyoming, appears to be 
nearest to Seleropages, and Brychaetus, from the Eocene (London 
Clay) of Sheppey, Kent, to Arapaima, so far as the state of pre- 
servation of these fossils enables us to form an opinion. 
Dr. Giinther has directed attention to the remarkable coin- 
HETEROTIS 
OSTFOGLOSSUM 
ARAPAYIVIA 
Fic. 336.—Distribution of the Osteoglossids. 
