142 TETRODOXTIDJE. 



Suborder X. PLECTOGNATHI. 



Air-bladder without open duct. Opercular bones more or less 

 reduced ; supraoccipital separating the parietals, in contact with the 

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

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

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

 Body covered with more or less osseous scales, bony scutes, or spines, 

 or naked. 



Fam. 1. TETRODONTIDiE. 



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

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

 sometimes connected with the operculum. First four or five preecaudal 

 vertebrae with bifid neural spine and closed neural arch. Supraclavicle 

 oblique, sometimes nearly horizontal ; lower three pectoral pterygials 

 enlarged and immovably united to the coraco-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. 



Seas of the 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. 142. 

 Dorsal and anal with more than 20 rays ... 2. Chonerhinus, Blkr., p. 148. 



1. TETRODON. 

 Linn. Syst. Nat. i. p. 410 (1766), part. ; Griinth. Cat. Fish. viii. p. 271 (1870); 

 Bouleng. Poiss. Bass. Congo, p. 502 (1901) ; Regan, Proc. Zool. Soc. 1902, 

 p. 294 ; Bouleng. Fish. Nile, p. 543 (1907). 



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

 20 rays. Vertebra 17 to 22. 



Four species in the fresh waters of Africa. 



Synoftsis of the Species. 



I. Eyes lateral ; caudal fin at least as long as or a little shorter than head. 



A. Caudal rounded. 



Caudal peduncle 1\ to H times as long as deep . 1. T. fahaka, L., p. 143. 



Caudal peduncle about twice as long as deep . . 2. T. mint, Blgr., p. 145. 



B. Caudal truncate 3. T. pustulatus, A. Murray, 



II. Eyes directed upwards ; caudal fin £ or a [p. 146. 



little more than 5 length of head ... 4. T. miunus, Blgr., p. 147. 



