HETEROTIS. 



83 



OSTEOGLOSSID^E. 



Margin of the upper jaw formed by the prsemaxillaries and the maxillaries, the 



latter the more developed ; nasal bones large and in contact with each other ; parietal 



bones separating the supraoccipital from the frontals ; suboperculum much reduced 



and entirely or partially concealed under the preeoperculum *. No pharyngeal teeth. 



Ribs inserted on the strong parapophyses ; epipleurals, no epineurals. Pectoral fins 



low down, folding against the body. Head scaleless, the thin skin confluent with the 



bones ; body covered with large bony scales, composed of pieces like mosaic. No 



oviducts. 



Fiff. 12. 



Skeleton of Heterotis niloticus. (After Hemprich & Ehrenberg.) 



This family is represented by four genera: Osteoglossum and Arap aima in South 

 America, Scleropages in Australia and the Malay Archipelago, and Heterotis in Africa. 



1. HETEROTIS. 



Sudis (non Rafinesque), part., Cuvier, Regne Anim. i. p. 180 (1817). 

 Heterotis (Ehrenberg), Cuvier & Valenciennes, Hist. Poiss. xix. p. 465 (1846). 

 Helicobranehus, Hyrtl, Denkschr. Ak. Wien, viii. 1854, p. 86. 



Mouth moderate, with small conical teeth forming a single series in the prae- 

 maxillaries, maxillaries, and dentaries ; groups of villiform teeth on the entopterygoids 

 and on the tongue. Branchiostegal rays 7 or 8. Body strongly compressed. Dorsal 



* Eor a detailed account of the craniological characters of this family, ef. Ridewood, Journ. Linn. Soc, 

 Zool. xxix. 1905, p. 252. 



m2 



