Page:Natural History, Mollusca.djvu/171

 there are three muscles given off from each piece to the succeeding one, one in the line of the back, the others at each side. Thus the animal may be considered as enveloped in a coat of plate armour, and the name of coat-of-mail shell is sometimes applied to it by collectors.

SHELL-PLATES OF CHITON.

The chiton has no projecting head, nor any tentacles, but a kind of veil that surrounds the mouth; the eyes also are wanting. There is a very long ribbon-like tongue, armed like that of the limpet, with horny teeth. The gills consist of small triangular leaflets, set in a fringe, which runs along the furrow between the mantle and the foot. The foot is large, and extends the whole length of the animal.

In the family are comprised two genera, differing in the development of the shelly plates.