142 TETKODONTID-E. 



Suboraer X. P L E C T O G N A T H T. 



Aii-blatUlcr without open duct. Opercular bones more or loss 

 reduced ; supraoccipital separating the parietals, in contact witli the 

 frontal ; maxillary and priBmaxillary bones often firmly united. No ribs. 

 Pectoral arch suspended from the skull ; no mesocoracoid. Ventral Hns 

 thoracic and much reduced, if present. Gill-opening much reduced. 

 l)()dy covered uith more or less osseous scales, bony scutes, or spines, 

 or naked. 



Fara. 1. TETRODONTIU.E. 



Teeth coalescent, forming a beak, with a median suture. luter- 

 operculum a long rod, attached to the inner face of the prfeoperculum, 

 sometimes connected with the operculum. First four or five pva^caudal 

 vertebriK with bifid neural spine and closed neural arch. Supraclavicle 

 oblique, sometimes nearly horizontal ; lower three pect(unl pterygials 

 enlarged and immovably united to tlie coraco-scapular cartilage ; ujipor 

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

 I'elvis absent. Gills three. Skin naked or with movable spines, rarely 

 with bony plates ; belly inflatable. 



Seas of tbe tropical and warm parts of the World, a few species 

 in fresh waters ; the latter represented in Africa by two genera : — 

 Dorsal and anal with less than 20 rays .... 1. Tetrodon, L., p. Ii2. 

 Dorsal and anal with more tlian 20 rays ... 2. Clionerliiitiif, Blkr., p. U8. 



]. TETRODON. 

 Linn. Syst. Xat. i. p. 410 (1761')), part.; Giintli. Cat. Fisli. viii. p. 271 (l.S7()); 

 BoulcMio-. Poiss. Bass. Cungo, p. 502 (1001) ; Kegan, Proe. Zoul. .Sue. 1;HI2, 

 p. 2lt-l ; Bouleng. Fish. Nile, p. 043 (11H)7). 

 Skin smooth or prickly. Dorsal and anal tins short, with less than 

 20 rays. Vertebr* 17 to 22. 



Four species in the fresh waters of Africa. 



SipiopHis of the Species. 



I. Eyes lateral ; caudal fin at least as long as or a little shorter tlian jieaii. 



A. Caudal roundeil. 



Caudal peduncle 1| to li times as long as deep . 1.7'. fnhala, L., p. 14.'?. 



Caudal peduncle about twice as long as deep . . 2. 7'. iithu, BIgr., p. 14."). 



B. Caudal truncate 3. T. inislulalus, K. 'SUwvwy, 



II. Eyes directed upwards ; caudal fin i or a [p. 14(;. 



little more than Hength of head ... 4. T. miurns, V>]'^v., \\ \\1 . 



