92 GASTROCH^ENIDJE. 



HABITAT : Southern coasts of England,, the Channel 

 Isles, South Wales, Barmouth, and the south and west 

 of Ireland, in 820 f. The variety was found by Mr. 

 Clark at Exmouth. Eed and Coralline Crag (S. Wood) ; 

 Italian tertiaries (Brocchi and Philippi). It does not 

 appear to be a northern shell; but it is tolerably 

 common on the coasts of France, Spain, Italy, Greece, 

 Algeria, Madeira, and the Canary Isles, at depths 

 between 2 and 60 f. 



This remarkable shell, as well as its animal and case, 

 were described by Montagu with his wonted accuracy. 

 He states that he had specimens not only in limestone, 

 but in granite ; and he modestly observes, " How the 

 siliceous part of this last is destroyed, we do not pretend 

 to determine." Cailliaud has ascertained that all the 

 lithophagous bivalves secrete a corrosive liquid, at least 

 in the months of May and June ; and, not content with 

 the usual test of litmus-paper, he tasted some of the 

 animals thus exemplifying the saying of Seneca (' De 

 vita beata'), "curiosum nobis natura ingenium dedit." 

 We are told by the French philosopher that the Gastro- 

 chcena affects the throat with an insufferably acrid flavour, 

 like that of a bitter cucumber. But the oyster, which 

 is not lithophagous, and Pholas are equally provided 

 with the same acid. This fact seems to militate against 

 the chemical theory. I have a cluster of a dozen 

 G. dubia in a single oyster-shell. The case or crypt is 

 thick and composed of a great many layers. The ex- 

 posed part of it is formed of tubercular concretions of 

 different shapes and sizes ; its neck resembles a double 

 cylinder joined together but open on the inner side, 

 and it is frequently curved. The anterior part of the 

 shell is evidently subject to much friction during the 

 process of excavation, and is invariably divested of the 



