270 PISCES. 



Two of the genera. Tetraodon and Diodon, have the faculty 

 of swelling themselves up like a balloon, by filling their sto- 

 mach, or rather a sort of very thin and extensible crop, which 

 occupies the whole length of the abdomen, and adheres closely 

 to the peritoneum, a circumstance which has occasioned it to 

 be considered at one time as the peritoneum itself, and at ano- 

 ther as a species of epiploon, with air. When thus inflated, 

 they roll over, and float on the surface, with the abdomen up- 

 wards, unable to direct their course; but they are extremely 

 well defended wiiile in this position by the erection of the 

 spines with which their skin is everywhere furnished.(l) 

 Their natatory bladder has two lobes, and their kidneys, which 

 are placed very high up, have been erroneously taken for 

 lungs.(2) They have but three branchiae on each side,(3) and 

 when captured they produce a sound which is occasioned by 

 the air rushing out of their stomach. Each of their nostrils 

 is furnished with a double fleshy tentaculum. 



Diodon, Lin. 



So called because the jaws are undivided and formed of one piece 

 above and another below. Behind ihe trenchant edge of each of 

 these pieces, is a round portion, transversely furrowed, which con- 

 stitutes a powerful instrument of mastication. (4) The skin is every- 

 where so armed with stout pointed spines, that when inflated, they 

 resemble the burr of a chesnut tree. A number of species inhabit 

 the seas of hot climates. 



Some of them have long spines supported by two lateral roots. 

 The most common of this group, Diod. atinga, Bl., 125, and 

 better, Seb., Ill, xxiii, 1, 2, is more than a foot in diameter. (5) 



(1) See Geoffroy-St-Hilaire, Polss. d'Eg., in the great work on that country. 

 A similar disposition is observable in Chironectes. 



(2) It is thus I explain the mistake of Schccpfer in the publications of the Nat. 

 of Berlin, VIII, 190, and that of Plumier, Schn. , 513, and doubtless that of Gar- 

 den, Lin. Syst., Ed. XII, i, p. 348. As to the cellular organs mentioned by 

 Broussonnet, Ac. des So., 1780, last page, there is nothing to be found which re- 

 sembles them. The process of respiration in these fishes is similar in all things 

 to that of others. 



(3) An instance of this we have already seen in Lophlus. 



(4) Fossil jaws of this description are not uncommon. 



(5) The Diod. histrix, Bl., 126, is the same species uninflated. To avoid all 

 equivocation, I call it Diodon pundaius; — Add Diod. spinosissimus, Cuv., Mem. 



