698 PLECTOGNATHI. 



Family, II— GYMNODONTES, Cuvier, 



Body more or less short. Some possess the means of dilating an elastic portion of the oesophagus, or 

 an abdominal sac, with air: or this power may be entirely wanting. Bones of the upper and lower jaw in 

 the form of a beak, having a cutting edge, and being covered with a layer of ivory-like substance in which a 

 median suture may be present or absent. A spineless dorsal, anal and caudal exist : pectorals present : 

 ventrals absent. Dermal covering modified into small or large spines or laminse. Pelvic bones and air-vessel 

 present or absent. 



Most of the Indian forms of fishes included in this family are reputed to be highly indigestible as 

 food or even virulently poisonous. 



SYNOPSIS OP INDIAN GENERA. 



First Group— Triodontina. 



Tail and caudal fin distinct. Abdomen dilatable into a large compressed sac, which is supported by 

 an elongated pelvic bone. Air-vessel present. 



1. Triodon. The upper jaw divided by a median suture : the lower jaw entire, p. 698. 



Second group — Tetbodontina. 



Tail and caudal fin distinct. A portion of the oesophagus dilatable and may be distended with air. 

 No pelvic bone. Air-vessel present. 



A. — Jaws with a median suture. 



2. Xenopterus. Dorsal and anal fins with many rays, p. 699. 



3. Tetrodon. Dorsal and anal fins with few rays, p. 699. 



B. — Jaws without any median suture. 



4. Diodon. A simple nasal tentacle having a pair of lateral orifices. Body covered with stiff movable 

 spines, p. 708. 



First group — Triodontina. 



Tail and caudal fin distinct. Abdomen dilatable into a large compressed sac, which is supported by 

 an elongated pelvic bone. Air-vessel present. 



Genus, 1 — Teiodon {Ueinw.^, Cuvier. 



BranoMostegals six. The upper jarv tvith, the loiver without, a median suture. Two separate nasal orifices 

 on either side. Tail elongated, terminating in a bilobed fin : dorsal and anal with few rays. Abdomen possessing a 

 large sac, the upper portion of which can be dilated u-ith air, whilst it is kept distended by elongated pelvic bones. 

 The dermal covering consisting of spinate, osseous la7nince, which are not imbricate. Air-vessel present. 



Geographical distribution. — The single species of this genus at present recorded, has been taken in the 

 seas of India and the Malay Archipelago. 



Triodon bursarius. 



(Reinw.) Cuv. Regn. Anim. ; GriiBth in Cuv. An. King, x, pi. x ; Bleeker, Blootk. p. 20, and Atl. Ich. 

 V, p. 84, t. ccxiv, f. 1 ; Giinther, Catal. viii, p. 270. 



Triodon macropterus, Less. Voy. Coq. Zool. pi. iv. 



B. vi, D. 10-11, P. 15-16, A. 9-10, C. 18. 



Length of head 4 to 4j, of caudal fin 7 in the total length. Eyes — situated in the posterior half of the 

 head. Interorbital space rather concave. Fins — dorsal situated in the last half of the distance between the 

 eye and the base of the caudal fin, and slightly in advance of the anal, both are highest anteriorly : caudal 

 emarginate. Colours — dull brown, a large, irregularly shaped, black yellow- or blue-edged spot is present on 

 the upper portion of the sac. Fins j'ellow. 



Habitat. — Seas of India tj thg Malay Archipelago. It attains at least 21 inches in length. 



Second group— Tetrodontina. 



Tail and caudal fin distinct. A portion of the oesophagus dilatable and may be distended with air. 

 No pelvic bone. Air-vessel present. 



