98 Mr Stark on Two Species of Pholas 



Art. XXI. — Observations on Two Species of' Pholas, found 

 on the Sea- coast in the neighbourhood of Edinburgh. * By 

 John Staiik, Esq. M. W. S. Communicated by the Au- 

 thor. 



The Natural History of the Pholades, so far as regards their 

 mode of burrowing in wood and stone, seems yet to be but 

 imperfectly understood, though the Pholas was known to the 

 ancients, and Pliny notices its phosphorescent quality. Ron- 

 deletius, Johnston, and Rumphius have figured several spe- 

 cies ; Lister, among others, gives representations of three 

 British species, the Pholas dactylus, Candida, and crispata ; 

 and Sir Robert Sibbald, in his Prodromus, has three rude 

 figures of the dactylus or crispata, as Scottish shells. None 

 of these authors, however, attempted to explain how the Pho- 

 lades excavated 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 parti- 

 cularly to this inquiry. In his work, entitled " Recreatio 

 Mentis et Oculi? the first edition of which, in the Italian lan- 

 guage, 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, showing, with considerable accuracy, the na- 

 ture of the perforations, and distinctly 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 purpose, 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 

 investigations of Bonanni, whose book is neither quoted nor 

 alluded to by the French naturalist. In the " Memoires de 

 r Academic Royale des Sciences 1 ' 1 for 1710, this intelligent ob- 

 server has a paper on the progressive movement of some spe- 

 cies of Bivalves; and in the volume for 1712 he gives the se- 



* This paper is an abstract of the original one, which will appear in 

 vol. x. part ii. of the Edinburgh Transactions- 

 { Bonnnni, Recreaf. p. 36. 



