FAMILY GYMNODONTIDE — DIODON. 323 
ORDER VI. PLECTOGNATHI. 
Gills and rays concealed beneath the skin. The maxillary bone 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 GYMNODONTIDz. 
Instead of the ordinary teeth hitherto observed in fishes, this family has the jaws furnished 
with a bony substance resembling enamel, divided internally into lamine ; these are 
essentially true teeth united together. The snout not produced. Inhabit chiefly tropical 
seas. Ilesh of several species poisonous. 
Ops. 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 with slender prickles or stout spines. 
Oss. 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 cesophagus. 
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 MACULATO-STRIATUS, 
PLATE LVI. FIG. 185. — (CABINET OF THE LYCEUM.) 
Diodon atinga, Sphericus aculeis triquetris. L.? 
Toad-fish at New-York, Scuarrr, Beobachtungen u. s. w. Vol. 8, p. 192. 
Diodon maculato-striatus, Spot-striped Diodon. Mircuiut, Lit. and Phil. Soc. Vol. 1, p. 470, pl. 6, fig. 3. 
Diodon rivulatus. Cuvier, Memoires du Museum d’Hist. Naturelle, Vol. 4, p. 129, pl. 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 
