PHOLAS STONE PIERCER. 197 



PHOLAS Candida* 

 WHITE STONE PIERCER. 



Specific character. Shell oval, obtuse, nearly 

 closed at the anterior end, thin, fragile, almost 

 transparent, striated transversely, and crossed 

 by finer stria? in a radiated form from the um- 

 bones, a few of the radii at the larger end set with 

 short spines ; hinge smooth and reflected, teeth 

 slender and curved ; one valve has a curved 

 lamina above the tooth ; there is a single acces- 

 sory valve ; the colour is yellowish white ; it is 

 about three-quarters of an inch long, and three 

 inches broad. 



These Pholades inhabit marine rocks ; they 

 are found in great numbers on the Devonshire 

 coast ; the stone in which they are imbedded is a 

 cementation of the finest sand and limestone ; 

 it is very soft when first taken from the bed, and 

 so absorbent as to afford sufficient moisture for 

 the purposes of life, and for the peculiar actions 

 of the mollusca. The animal secretes a mild 

 phosphorescent solution, which would be of suf- 

 ficient power to decompose the rock by the slow 

 contact of its gradually increasing bulk. 



* Plate X. figure 8, 



17* 



