MULTIVALVES. PHOLAS. 25 



shell is usually of a pure or dusky-white: however, the 

 absence of color is amply compensated for by the beau- 

 tiful fret-work with which the shells of this genus are 

 adorned. 



In some species the reticulations are so delicate in their 

 fabric, as to resemble the finest lacej in others the tex- 

 ture is coarser, and approaches nearer to small basket- 

 work; and in the Pholas costata, the shell is covered with 

 regular, elevated, jagged, or scolloped ribs, so elegantly 

 disposed, as to render it no less desirable for its beauty 

 than its scarcity. 



The Pholades are found in company, but not in groups 

 or clusters, as the Lepades are ; for each individual Pholas 

 is detached from its neighbour, and occupies a separate 

 and distinct habitation, which it forms for itself, by ex- 

 pressing a coroding juice, in any substance which acci- 

 dent or intent has made most eligible. 



Stone, clay, wood, sponge, coral, equally serve as ha- 

 bitations for the Pholades; even the stoutest oak planks 

 of ships' sides are pierced by them with the greatest fa- 

 cility. As they advance in growth, they enlarge their 

 habitation within, leaving the small aperture, by which 

 they originally entered, of its primitive dimensions, there- 

 by precluding all possibility of a retreat. 



The animal possesses the property of emitting a phos- 

 phorescent liquor, which shines with brilliancy in the 

 dark, and illuminates whatever it touches. 



The American, Indian, and European seas supply the 

 few species that are known. 



Late discoveries have proved the existence of fossil 

 Pholades, called Pholadites. 



