LAMELLIBRANCHIA. 43 
disturbed, bore with such rapidity and to such a depth that their 
capture is a matter of great difficulty ; and even when seized they 
hold on so tightly that at times they suffer their foot to be torn off 
rather than be captured. They not only burrow in sand, but also 
have the power of darting through the water, like the Scallops. 
Solens were considered a dainty dish by the ancient Greeks, and 
numbers are still eaten by the poorer coast-population of this 
country and abroad. 
The Pholadidm, or Piddocks, are very remarkable shells, of an Cases 201- 
unusually complicated structure, some having the power of boring 
into rocks, wood, mud, sand, etc. Their shells are white, adorned 
with prickly sculpture, and, although thin, are strong. The foot is 
believed to be the principal excavating instrument, but the shell no 
doubt is used as a file to enlarge the hole as the creature grows. 
These animals are brightly phosphorescent ; and certain species are 
eaten at many places on the shores of the Mediterranean. They 
202. 
2 
Piddock, or Borer (Pholas dactylus). (From the British coast.) 
1. Animal in the shell: a, foot; b, siphons; c, inhalant orifice; d, exhalant 
orifice. 
2. Shell : e, accessory valves or plates. 
appear to be indifferent as regards the material they bore into ; for 
the common Pholas dactylus (Fig. 36) of our own shores has been 
found in slate-rocks, mica-schist, coal-shale, new red sandstone, 
chalk, marl, peat, and submarine wood. The siphons are long in the 
Piddocks, united except near the end, and enclosed in tough skin. 
The species are world-wide in their distribution, and several are 
found fossil in some of the Tertiary formations. 
The Teredinidoz, or Ship-worms, are also borers, like the Pholads, Ca se 202. 
but do not perforate rocks. They are principally wood-borers ; the 
large Kuphus arenaria, which is an exception, living buried in the 
sand. The ship- worm has a long worm-like body, from 6 to 12 
