35if Natural History of Molluscous Animals ; — 



immerse themselves in cells, whence they cannot again issue 

 or be removed ; their house during life, and after death their 

 grave. The Teredo digs his tortuous cell in wood ; the Pho- 

 lades construct their more capacious dwellings in wood or 

 clay; the Lithophaga and Lithodomi excavate limestone rocks, 

 coral rocks, or the thick shells of other Mollfisca ; while the 

 Fistulanae are said to burrow indifferently in sand, in wood, 

 in rocks, and in shells. In general each species confines itself 

 to one kind of substance, though this is not always the case. 

 Olivi says that he has twice seen Pholades in a piece of com- 

 pact lava ; the common European species of that genus are 

 found as often in timber as in clay, and some of them per- 

 forate likewise calcareous rocks. Montagu tells us he had 

 specimens of Mya pholadia in common limestone, in fluor, 

 and in granite * ; and Dr. Pulteney speaks of Donax Trus as 

 being plentiful on the Dorset coast in clay as well as in lime- 

 stone.f They are to be found on all shores, from Greenland 

 to the furthest Ind. Within the tropics, however, they are 

 most abundant, and of the largest size ; but the station most 

 celebrated in history is European, viz. in the Bay of Naples, 

 where a colony of Lithodomi had settled themselves in the 

 pillars of the temple of Jupiter Serapis during the period of 

 its submersion. At the height of 10 ft. above the base of the 

 three standing pillars which remain, and in a position exactly 



corresponding in all, is a zone of 6 ft. in height, where the 

 marble has been scooped into cells by these Mollusca (Jig. 61). 



* Test. Brit. Sup., p. 21. 



t Ibid, p. 109. 



