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III. Notice on a peculiar Properti/ 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. 



The 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 etiected. While some are disposed to 

 regard these cavities as the result chietiy 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. 



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 



