TETEODON. 



543 



PLECTOGNATHI. 



TETRQDONTID^. 



Teeth coalescent, forming a beak, with a median suture. Interoperculum a long 

 rod, attached to the inner face of the prseoperculum, sometimes connected with the 

 operculum. First four or five praecaudal vertebrae with bifid neural spine and closed 

 neural arch. Supraclavicle oblique, sometimes nearly horizontal ; lower three pectoral 

 pterygials enlarged and immovably united to the corneo-scapular cartilage; upper 

 pterygial small, suturally united to the scapula. No spinous dorsal fin. Pelvis 

 absent. Gills three. Skin naked or with movable spines, rarely with bony plates ; 

 belly inflatable. 



1. TETRODON. 



^innseus, Syst. Nat. i. p. 410 (1766), part. ; Giinther, Oat. Fish. viii. p. 271 (1870) ; 

 Boulenger, Poiss. Bass. Congo, p. 502 (1901). 



Skin smooth or prickly. Dorsal and anal fins short, with less than 20 rays ; 

 vertebra 17 to 22. 



Fig. 41. 



Skeleton of Tetrodon fahaha. § nat. size. 



This genus comprises a large number of species, which are mostly marine. Four 

 species are represented in the fresh waters of Africa, viz. : — T. faliakq, L. (Nile, 



