CHAPTER V.—Borine BIVALVEs. 
The Piddocks (Pholadide) and 
the Ship Worms (Teredide) are 
more especially adapted for bor- 
ing in wood, hard mud or stone 
than any other mollusks. 
Fig. 29. Pholas truncata. 
Fragments of the largest one 
of these, Pholas costata Linn., 
are frequently found on the beach 
after storms; but living speci- 
mens can only be had by dredg- 
ing. Rarely perfect valves are 
thrown up. It is a most beauti- 
fully sculptured shell, pure white 
in color. The margin of the 
se ; 
Fig 28. Pholas costata. valves is turned outward over 
the beaks and there is a slender curved arm projecting from 
under the beaks. 25 
