Page:Natural History, Mollusca.djvu/170

158 Mr. Patterson, when residing, in July, 1837, near the town of Larne, in the county of Antrim, endeavoured to form some calculation of the quantity of limpets alone taken from the rocks about that part of the coast, and used as food. He had reason to believe that the weight of the boiled "fish" was above eleven tons! The weight, as carried from the beach, was, however, much greater, as there was to be added that of the shell, and the seawater which it contained. This, too, was exclusive of a probably equal quantity of periwinkles and whelks.

We find in this family a group of mollusca, which, possessing in their anatomical structure nothing very peculiar, present, in the covering by which they are protected, a form of shell quite anomalous, and such as to have given rise to a conjecture that in this family we have the link that connects the with the.

The shell in the chitons consists of eight narrow transverse calcareous pieces, overlapping each other, and strongly implanted in a thick and fibrous border of the mantle, which surrounds the whole. The mantle itself is of a stiff leathery consistence, and though sometimes smooth, is more commonly covered with small scales, spines, or hairs. The elasticity of this investiture allows the animal to stretch and contract itself in crawling, and even to roll itself in a ball, in the manner of an oniscus or a hedgehog, the shelly pieces moving freely upon each other. To effect the various motions required,