248 FUNCTIONS AND INSTINCTS. 



which he denominates Saxicave* and Petri- 

 cole? the habits of which appear to be the same. 

 M. Fleurian-de-Bellevue has described the pro- 

 ceedings of a species found in great numbers in 

 submarine calcareous rocks near Rochelle. It 

 lives like the pholads in crypts within the rock, 

 but as the crypt is not circular, it is clear 

 it cannot be produced by a revolution of the 

 animal upon its foot ; M. de Bellevue, therefore, 

 concluded that it dissolved the stone by means 

 of a phosphoric acid transuding from its body. 

 Some have thought, that did the animal secrete 

 such an acid, it must have destroyed its shell, 

 but since the rock round the crypt is found to 

 be differently coloured from the rest, for a little 

 thickness, and the animal does not frequent the 

 argillaceous, basaltic, and other rocks in the 

 vicinity, but only the calcareous ones, M. Bel- 

 levue's opinion is rendered not improbable. It 

 is surely very possible that the acid may be so 

 mixed and tempered as to act upon the rock 

 and not upon the shell. Mr. Osier, in the 

 memoir lately quoted, brings forward some very 

 powerful additional arguments which confirm 

 this opinion. The species which he observed 

 was the rugose saxicave. 3 This animal fixes 

 itself by a byssus from the foot, and therefore 

 cannot perform a rotatory motion, and it appears 



1 Saxicava. 2 Petricola 3 Saxicava rugosa. 



