THE 



QUARTERLY JOURNAL 



OF 



CONCHOLOGY. 



BURROWING AND PERFORATING MOLLUSCS. 

 By W. D. SUTTON. 

 Prominent amongst this class may be named the ^^ Plwlas Dae- 

 J{ \ It an examination be made at low water of such portions of 

 the chalky rocks and white cUffs of which this island is composed 

 more especially those portions which run M^ell out to sea, they will 

 trequently be found to be perforated with numerous holes, which run 

 to a considerable depth, and vary considerably in theii- dimensions. 

 Ihese holes are made by that remarkable little animal the ^^ Pholas 

 nactylus. ^ It does not appear to be clearly ascertained how the 

 operation is performed, and it is all the more wonderful how hard 

 rocks and timber can be so perforated, seeing that the shell of the 

 animal is by no means hard, and capable of acting as a file. How- 

 ever, lor the sake of argument, taking it for granted that the shell 

 was used as a boring tool, then the hole made would be nearly 

 cu'cular instead of, as is really the case, being accommodated to the 

 shape of the shell. Few materials are proof against their ravages, 

 and such hard substances as oak, sandstone, limestone, or chalk, 

 frequently form then- habitations, and it is a well-known fact that 

 such solid stone as the Plymouth breakwater was very soon attacked 

 by these creatures. They are particularly obnoxious to the con- 

 sti'uctors of wooden piers, and very soon reduce to a honeycombed 

 state the submerged portions of the piles, and the only way to protect 

 the same with any degi-ee of immunity from their ravages is to drive 

 iron nails closely into the submerged portions, and they wUl bid 

 defaance to the Pholas, as they cannot pierce ii-on. The best method 

 ot obtammg good specimens of the shells is by splitting open the 

 piece of rock, and thus extracting them without injury from the rocky 

 homes where they have lived and died. A curious projection is 

 observable m the interior of a perfect shell, in appearance somewhat 

 resemblmg a spoon ; but what may be the objectof this is somewhat per- 

 plexing. The tube, which has been mentioned, generally consists of 

 a composite organ composed of two tubes (or as they may be not 

 mappropriately styled siphons), which are placed in close proximity 

 together, resembling in principle a double-barrelled gun. The water 

 which IS necessary for theh- respiration passes through these tubes, 



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