64 
ROOM XI. 
Nat. Hist. 
has usually a musky odour, is said to be deleterious at 
particular seasons. Several of these fishes have the fa¬ 
culty of dilating their stomach with air, giving the body 
the appearance of a balloon. When this takes place 
they float along the surface of the water, belly up¬ 
wards. The Diodons ( Diodon ) have both jaws undi¬ 
vided, and their skin armed with large spines. The skin 
of some species of this genus is used as a kind of helmet 
by the Chinese. The Tetrodons ( Tetraodon ) have 
the jaws divided in the centre by a perpendicular suture, 
and the skin covered with small, slightly prominent 
spines. The Triodons ( Triodori ) have the skin of the 
Tetrodons, but the upper jaw r alone is divided, so that 
they appear to have three teeth. 
The Moon Fish, or Molae ( Orthagoriscus ), have the 
same kind of jaws as the Diodons, but the body is 
compressed and without spines, and not susceptible of 
being inflated; and the tail is so short and high, that 
they have the appearance of being merely the head of 
a larger fish. 
The family of File Fishes ( Balistidce ) have their jaws 
armed with a small number of distinct teeth ; their skin 
is hard, and their head produced, ending in a small 
mouth. They are divided into several genera, accord¬ 
ing to the structure of their outer covering. The true 
File Fish ( Batistes ) has a compressed body, covered 
with hard scales, and the first dorsal fin has spinous 
rays; its colours are brilliant, but its flesh is said to be 
unwholesome. It is chiefly found in the Torrid Zone, 
living upon sea-weeds. Others, as the Unicorn File 
Fish ( Monacanthus ), have the skin covered with small, 
hairy scales, and the first dorsal fin has only one spine. 
The Three-spined File Fish ( Triacanthus ) has a silvery 
skin covered with small scales, and a ventral fin, con¬ 
sisting of a single spine, on each side. 
The Trunk Fish ( Ostracion) has the same elongated 
form as the Three-spined File Fish, and the body 
covered with an inflexible case formed of regular bony 
compartments. It has a very large liver, which yields a 
considerable 
