OSTEOGLOSSLD^. 377 



Fam. 20. OSTEOGLOSSIDiE. 



Body covered with large hard scales, composed of 

 pieces like mosaic ; head scaleless, its integuments 

 nearly entirely replaced by bone; lateral line com- 

 posed of wide openings of the mucus-duct. Margin 

 of the upper jaw formed by the intermaxillaries mesi- 

 ally, and by the maxillaries laterally. The dorsal fin 

 belongs to the caudal portion of the vertebral column, 

 is opposite and very similar to the anal fin ; both ap- 

 proximate to the rounded caudal (with which they are 

 abnormally confluent). Gill-openings wide ; pseudo- 

 branchiae none ; air-bladder simple or cellular. Sto- 

 mach without csecal sac ; pyloric appendages two. 



Large freshwater fishes of the tropics. 



Synopsis of the Genera. 



Barbels two ; abdomen trenchant 1. Osteoglossum, p. 377. 



Barbels none ; abdomen rounded ; teeth anteriorly on the palate. 



2. Ahapaima, p. 379. 



Barbels none ; abdomen rounded ; palate smooth anteriorly. 



3. Heteeotis, p. 379. 



1. OSTEOGLOSSUM. 



Osteoglossum, VandelU; Agassiz. 



Ischnosoma, Spix, Pise. Bras. p. 46 {see Heterotis niloticus, p. 380). 

 Scleropag-es, Giinth. Axti. ^ Mag. Nat. Hist. 1864, xiv. p. 196. 

 Anatomy : see Hyrtl, Denkschr. Ak. Wiss. Wien, viii. 1855, in Me- 

 moir on Heterotis. 



Body more or less elongate, compressed, with the abdomen com- 

 pressed into a trenchant edge ; cleft of the mouth very wide, obhque, 

 with the lower jaw prominent. A pair of barbels at the lower jaw. 

 Maxillary very long, styliform, scarcely protractile. Jaws with a 

 series of small teeth ; bands of rasp-like teeth on the vomer, pala- 

 tine and pterygoid bones, on the tongue and hyoid. Pectoral fins 

 elongate. Gill-membranes nearly entirely separate ; branchiostcgals 

 rather numerous ; air-bladder simple. (Stomach without blind sac ; 

 two pyloric ajjpendages. 



Fresh waters of tropical America, Australia, and of the East-Indian 

 archipelago. 



