Jbwnd on the Sea-coast near Edinburgh. 99 



quel of his observations on this curious subject. In this se- 

 cond memoir, after detailing the manner in which the Solenes 

 burrow in the sand, he is led to consider the means by which 

 the Pholas perforates the softer rocks ; and this, he endea- 

 vours to prove, is done merely by the actionof its muscular foot. 

 The hardness of the substance perforated, however, induces 

 M. de Reaumur to form a theory to account for an instru- 

 ment, so apparently unsuitable, being able to perform what 

 he ascribes to its action. The clay rock from the coast of 

 Poitou and Aunis, on which his observations seem to have 

 been made, was too hard on the surface to admit, in his mind, 

 the supposition of its being bored by such an implement ; and 

 he therefore concludes, that the Pholades must have entered 

 the clay when it was in a soft state, and that it had been subse- 

 quently hardened or petrified by some viscous quality of the 

 waters of the sea. This theory, it may be remarked, leaves 

 no room for the multiplication of the species ; for, on the 

 supposition that the clay has been hardened on the surface by 

 some petrifying quality of the water, after the Pholades had 

 made their lodgement, the same cause would operate to pre- 

 vent the future races from commencing their cells. * 



D'Argenville, with the knowledge, it appears, of what Bo- 

 nanni and Reaumur had written upon the subject before him, 

 next professes to give an account of the manner in which the 

 Pholades perforate their dwellings ; but, from the contrariety 

 of his statements, and his completely misunderstanding one 

 of the authors quoted by himself, little reliance is to be placed 

 upon his authority as an observer. In one passage of his 

 Zoomorphose, when describing the shell of the Pholas dacty- 

 litis, he says it resembles a file, with elevated striae and aspe- 

 rities, dentated and crowded from the top of the shell to its 

 base, in such a manner that the strongest points are towards 

 the head. " It appears," says he, " that with these arms it 

 pierces the stones, and enlarges its tomb as it increases in 

 size." But, in a passage a little afterwards, he adds, with a 

 strange forgetfulness of what he had previously written, " In 

 proportion as this animal grows, it digs its hole with a round 

 and fleshy part like a tongue ; and it is not with its two 



* Mrm. de I' Acad. Roy. des Sciences, 1712, p. 127. 



