45 
PH OLA S. 
(See Plate III. Fig. 4.) 
Shell bivalve, insequilateral, divaricate or gaping, 
beaked ; having smaller accessory valves situated 
upon the hinge and posterior slope. Hinge re- 
curved, furnished with a tooth. 
The Pholades, as their name, derived from the 
Greek (pooXsw, imports, seek a hiding-plac^ in all 
descriptions of rocky fragments, and even in wood, 
piercing the substance while they are young, and 
gradually increasing the dimensions of their cell 
according to their growth. The largest species 
and the finest specimens are most frequently found 
in chalk, which being the softest of calcareous 
rocks, admits, perhaps, of a more easy and rapid 
progress, than the indurated stones in which they 
are sometimes discovered. It is not, however, yet 
understood by what instrument they are enabled 
to penetrate the substance of their future prison ; 
when, judging from the size of the aperture, they 
are still in a young and, probably, a feeble state. 
