III. Notice on a peculiar Property of a Species of Echinus. 
By E. T. Bennett, Esq. F.L.S. Communicated by the Zoo- 
logical Club of the Linnean Society. 
Read June 21, 1825. 
Tux property of forming for themselves habitations or cells in 
stone or other hard substances, with which Nature has endowed 
certain of the less perfect animals, has repeatedly excited the 
investigation of zoologists, who are yet divided in opinion as to 
the means by which it is effected. While some are disposed to 
regard these cavities as the result chiefly of chemical action, 
others consider them to be produced by mechanical powers 
alone. Into this extensive question it is by no means my inten- 
tion to enter: I merely propose to put on record, for future and 
more able inquirers, a fact which has recently come to my 
knowledge, and which is new to those scientific friends whom I 
have consulted respecting it. - 3 
On the surface of a fragment of rock from the coast of the 
county of Clare, for which I am indebted to the kindness of Mr. 
J. D. Humphreys of Cork, there exist numerous depressions or 
cavities, occupied by a species of Echinus, and evidently formed 
by it, as they severally correspond in size with the stage of 
growth of their respective inhabitants. The fragment, which is 
about eight inches in length by six in breadth, contains in less 
than one half of its surface six of these cavities,—each of which 
is circular,—agreeing in form with that of the Echinus which 
occupies 
