22 MULTI VALVES. PHOLAS. 



and either inclines to a pure or dusky-white, or else a 

 sort of blueish or yellowish-brown tint is spread over it: 

 however, the absence of color is amply compensated for 

 by the beautiful fret-work with which shells of this ge- 

 nus are adorned. 



In some speciesthe reticulations are so delicate in their 

 fabric, as to resemble the finest lace; in others tlie 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 ele- 

 gantly 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 in the Lepades; for each individual Pho- 

 las is detached from its neighbour, and occupies a sepa- 

 rate and distinct habitation, which it forms for itself, by 

 expressing a corroding juice, in any substance which 

 accident or intent had made most eligible. 



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

 bitations for the Pholades; even the stoutest oak planks 

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

 lity: and as they advance in growth, they enlarge their 

 habitation within, leaving the small aperture, by which 

 they originally entered, of its primitive dimensions, 

 thereby precluding all possibility of a retreat. 



The animal possesses the property of emitting a \A\os~ 

 phorescent liquor, which shines with brilliancy in llie 

 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 Phohidjtes. 



