100 Mr Stark on Two Species of Pholas 



valves, nor with its teeth, that it performs this operation." 

 Further on he remarks upon another species, that it " is arm- 

 ed at its extremity with two strong and cutting points, in form 

 of an auger, of which the dentated contour gives it the means 

 of turning upon itself, and of piercing the stone downwards. 

 The stria; and the teeth do the rest.'' 1 * 



Among the more modern writers, Pennant mentions having 

 frequently taken the Pholades " out of the cells they had 

 formed in hard clay, below high water-mark, on many of our 

 shores. They also perforate the hardest oak-plank that is 

 lodged in the water. The bottoms of the cells,'" adds this 

 acute observer, " are round, and appear as if nicely turned 

 with some instrument.' 1 '' "f Montagu, speaking of the Mya 

 P/ioladia, says, " It is probable this, as well as similar animals 

 whose habits are to perforate stone, are provided with an acid, 

 or some other solvent menstruum capable of performing that 

 office." And, in another passage, he observes, " The Pho- 

 lades are performing similar works assigned by nature on soft- 

 er substances, such as chalk, indurated clay, and wood, which, 

 in like manner, are perforated by some solvent power :■— not 

 by the thin fragile shells that cover such animals, as some 

 have erroneously asserted and is too generally credited." -f- 



A late writer, Mr Wood, supports something like the same 

 theory ; at least he seems to think that the attrition of the 

 shell is insufficient for the effect produced ; " since,' 1 says he, 

 " there are some species, and particularly the P. orientalis, 

 which are nearly smooth at the anterior end, and, consequent- 

 ly, unfit for such a purpose ;" § while Mr Gray, in the Zoo- 

 logical Journal, gives it as his opinion, that the Pholades 

 " appear to bore by means of rasping.'" || 



Such are the discordant opinions that have been held re- 

 garding the mode by which the Pholades perforate calcareous 

 stones and wood : one class of naturalists asserting that they 



• L'Hist. Nat. eclaircie dans nne de ses parlies principalis. — Zo<jmor~ 

 phase, p. 69, 70. Paris, 1757. 

 t British Zoology, vol. iv. p. 158. 

 + Tcstacea Brilannica, p. 560, 561. 

 $ General Conchology, vol. i. p. 74. 

 I| ZoologicalJournal, No. 3. p. 406. 





