TETRODON, in ichthyology; a genus of fishes arranged by Linnaeus under the class of amphibia, and order of nantes; but placed by Gmelin under the class of pisces, and order of branchiostei. The jaws are bony, stretched out, and cloven at the point; the aperture of the gills is linear; the body is muricated beneath, and there are no ventral fins. There are 13 species: of which the most remarkable is the lineatus, called by Mr Hasselquist fabaka, which is the Egyptian and Arabic name. It has of late been found in the Nile about Cairo, but was never known in former times. It is said to grow to a prodigious size. When just caught, it pricks the skin if it is taken in the bare hands, and produces small pustules in the same manner as nettles. The flesh is poisonous. Mr Forster confirms the account of the poisonous nature of a species of tetrodon, in his account of New Caledonia.