FAMILY GYMNODONTID^ DIODON. 323 



ORDER VI. PLECTOGNATHI. 



Gills and raijs concealed beneath the skin. The maxillanj hone soldered to the side of the 

 intermaxillary, which alone forms the jaw- The palatine also soldered to the cranium. 

 Branchial aperture a narrow fissure. 



FAMILY GYMNODONTIDjE. 



Instead of the ordinary teeth hitherto observed in fishes, this family has the jaws furnished 

 with a bony substance resembling enamel, divided internally into lamina;; these are 

 essentially true teeth united together. The snout not produced. Inhabit chiefly tropical 

 seas. Flesh of several species poisonous. 



Obs. About sixty species have been described of this family. 



GENUS DIODON. Linneus. 



All the teeth united into a single one in each jaw. Behind the trenchant edge of each, a 

 rounded part furrowed transversely, and aiding in mastication. No ventral fins. Skin 

 furnished toith slender prickles or stout spines. 



Obs. The species of this and the following genus possess the singular property of puffing 

 themselves up into a globular ball, and in this state, float on the surface. This is effected by 

 swallowing the air, which is retained by a thick contractile muscle surrounding the oesophagus. 

 This condition, with the projecting spines, serves as a means of defence. Air-bladder with 

 two lobes. Kidneys placed high up, and have been mistaken for lungs. Liver occupies the 

 whole length of the abdomen, and divided into many small lobes. The jaws of this genus are 

 not unfrequently found in a fossil state, but I have not observed them in the United States. 



THE SPOT-STRIPED BALLOON-FISH. 



DiODON MACDLATO-STRUTDS. 



PLATE LVI. FIG. 185. — (CABINET OF THE LYCEUM.) 



Diodon atinga, Sphertcus aculeis triquetris. L. ? 



Toad-fish at New-York. ScHCEPFF, Beobachtungen u. s. w. Vol. 8, p. 192. 



Diodon macnlato-striatus. Spot-striped Diodon. MiTCHiLL, Lit. and Phil. Soc. Vol. 1, p. 470, pi. 6, fig. 3. 

 Diodon rivulatus. Cdvier, Memoires du Museum d'Hist. Naturelle, Vol. 4, p. 129, pi. 6. 



Characteristics. Greenish, with numerous meandering olive brown stripes, and a few dark 

 colored large blotches margined with green. Tail even. Length five to 

 seven inches. 



Description. Body subcubical. Front abruptly descending. Space between the orbits 



