158 CYCLOBRANCHIATA.—CHITONIDZA. 
Mr. Patterson, when residing, in July, 1837, near 
the town of Larne, in the county of Antrim, en- 
deavoured 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 sea- 
water which it contained. This, too, was exclusive 
of a probably equal quantity of periwinkles and 
whelks. * 
FAMILY CHITONIDA. 
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 MoLuusca with the ARTICULATA. 
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, 
* Introd. to Zool. i. 171. 
