Mr STARK on Two Species of Pholas. 429 



vated their habitations in the rock, or perforated the submerged 

 wood in which they seek protection. BONANNI, so far as I know, 

 was the first who turned his attention particularly to this in- 

 quiry. In his work, entitled " Recreatio Mentis et Oculi," the 

 first edition of which, in the Italian language, was published at 

 Rome in 1681, he has given figures of the Pholas dactylus, and 

 of pieces of the rock in which it was contained, shewing, with 

 considerable accuracy, the nature of the perforations, and dis- 

 tinctly marking the circular lines at the base of the cells. These 

 perforations are formed, in his opinion, by the action of the file- 

 like valves on the stone, the animal fixing itself, for this pur- 

 pose, by its callous foot to procure the necessary motion of its 

 shell *. 



The celebrated M. de REAUMUR next took up the subject, 

 without, however, seeming to have been aware of the prior in- 

 vestigations of BONANNI, whose book is neither quoted nor allud- 

 ed to by the French naturalist. In the " Memoires de 1'Aca- 

 demie Roy ale des Sciences" for 1710, this intelligent observer 

 has a paper on the progressive movement of some species of Bi- 

 valves; and in the volume for 1712 he gives the sequel of his 

 observations on this curious subject. In this second memoir, af- 

 ter detailing the manner in which the Solenes burrow in the 

 sand, he is led to consider the means by which the Pholas per- 

 forates the softer rocks ; and this, he endeavours to prove, is done 

 merely by the action of its muscular foot. The hardness of the 

 substance perforated, however, induces M. de REAUMUR to form a 

 theory to account for an instrument, so apparently unsuitable, be- 

 ing able to perform what he ascribes to its action. The clay 

 rock from the coast of Poitou and Aunis, on which his observa- 

 tions seem to have been made, was too hard on the surface to 

 admit, in his mind, the supposition of its being bored by such 



* BONANNI, Recreat. p. 36. 



