254 



POPULAR CONCHOLOGY. 



destructive to piers or wooden buildings under water. 

 The breakwater at Plymouth, soon after its erection, was 

 attacked by Pholades : it is constructed of limestone.* In 

 order to counteract their operations, nails are closely 

 driven into piles that lie under water, as is the case with 

 the pier at Southampton. 



The generality of the shells of this species are milky 

 white, and elegantly marked with rows of small prickles : 

 the animals are not used in this country as food, but on 

 the shores of the Mediterranean, where some large species 

 are found, they are not uncommonly eaten. When they 

 are irritated, they are said to throw out a stream of water 

 to a considerable distance. 



The animal is phosphorescent; this fact is mentioned 

 by Pliny, as well as by modern authors. The liquid 

 shines with uncommon splendour in the dark, and 

 illuminates whatever it touches or happens to fall upon. 

 ee It illuminates the mouth of the person eating it, and 

 is more lmninous the fresher it is ; when dry its light 

 will revive, on being moistened with salt water or 

 fresh ; brandy extinguishes it. " f Forbes says, this 

 luminous mucous is thrown off into the water, so that 

 the currents proceeding from the animal are luminous. 



This genus inhabits the European, American, and 

 Indian seas. 



Philippi enumerates the following as sub-genera : 

 Barnea Risso ; Martesia Leach ; Pholadidea Turton. 



Jouannetia. Desmoulins. (Triomphalia Sow. ; Pho- 

 ladopsis Conrad. — Shell globular, having behind a tail- 

 formed appendage ; the spoon-shaped processes of the 



* Penny Cyclopaedia, art. Pholas. 

 f Priestley's Optics. 



