IS an univalve shell-fish, the shape of which is pyramidal; it adheres to the rock with such strength that no human force can make him leave his hold, unless it is crushed by a strong blow. The apex of the shell is sometimes sharp, sometimes obtuse, and often surrounded with points and sharp prickles. When cleaned by proper means the shell is found sometimes of a beautiful purple tint, sometimes emits rays of reflected light of an uncommon brilliancy. They are found on the rocks, which are incessantly beaten by the surges and breakers on the sea shores of almost every country in the world. The rays of variegated colours which issue from their centre-tops, are sometimes found of the most vivid colours, and the animal that lives under this magnificent roof and versicolor canopy, is a kind of slug as disagreeable to the eye for his shape, as its flesh is for its taste insipid to the palate. It is not by any glutinous liquid, as it has been asserted, that this fish adheres so strongly to the rock but by the simple process of sucking the air between its body and the ground, to which it affixes itself.
The variety which Providence has thrown into the sum of animated beings is so wonderfully great, that Naturalists have reckoned thirty-six species of this genus of shell-fish; the difference arises merely out of the diversity of forms and colours.