hill — roisoxors rising. 221 
The Ostraciones, or Trunk-fishes, in lieu of scales, have 
an envelope made up of regular compartments^ set one into 
the other, and forming an inflexible coat of mail. It so 
invests the head and body, that they have nothing soft or 
moveable but the tail, the fins, the mouth, and the coria- 
ceous edging of the gill-slits. All their swimming appen- 
dages are passed through holes in their cuirass. The 
greater number of their vertebrae are cemented together, 
and their ten, or a dozen, conical teeth can break shells and 
Crustacea with ease. It will be seen that the Ostraciones 
have a close relation in external character with the Balistes. 
To what extent we are to place reliance on the assertion 
that the flexible portions of the fish are poisonous, especi- 
ally the tail, I know not ; but inasmuch as their flesh is 
but small in quantity, and their liver large, yielding oil 
considerably, and their stomach membranous and volumi- 
nous, they have not been suspected without reason of being 
poisonous. They are, with the Balistes, all tropical fishes. 
The Diodons and Tetraodons are fishes of the family 
Gymnodontidce. They both live on Crustacea and fuci. Their 
flesh is mucous or slimy. They have a peculiar organiza- 
tion— a detached outer skin, a sort of crop, which they can 
inflate, swimming upsidedown. Their air-bladders are very 
large. The stomach of the Diodon is thin, furnished with 
many appendages which, like so many small caecal pouches, 
contribute to the necessary completion of digestion, by re- 
tarding the aliment till it be acted upon by an augmented 
quantity of gastric juice. Their liver, thick and trilobate, 
extends almost to the anus. 
The flesh of both, Diodon and Tetraodon, is regarded as 
dangerous food. il Bison assures us that the gall is poison- 
