110 Beautiful Shells. 
are mysteries. The most common of them, perhaps, 
is the Prickly Pidduck, or Peckstone (P. dactylus), 
which is much used by the fishermen of our coasts 
as bait; the specific name is the Latin for a fruit 
shaped like a finger, which is something like the 
shape of this mollusk, as will be seen by the 
annexed engraving. 

The genus Pholus is very widely distributed, 
and all the species have the same boring habits as 
those of our own coast, which we need not enume- 
rate. Like them, too, in this respect, are the 
marine worms called Teredo, which make their way 
into the bottoms of ships, and all submerged timber, 
but these will be more fully spoken of in another 
volume. The above figure exhibits the Pholas dac- 
tylus as it appears in a section of rock, split open 
for the purpose of seeing the shelly miner at his 
work. 
