Gapers^ Piddocks^ and Ship-worms 1 69 



animal has long and 



nectinof link on one side with the forefroino^ Piddocks, 

 and on the other with the destructive Ship-worm 

 {Teredo), yet to be mentioned. The shell is like that 

 of a Pholas, but remarkably abbreviated, being in 

 fact globular in shape. It is glossy and almost 

 transparent ; crossed near the front end by a furrow 

 with marginal ridges. There are two dorsal shields, 

 similar to those of the Paper Piddock, but propor- 

 tionately larger. The globular 

 slender siphons, connected 

 throughout the greater part 

 of their length, and marked 

 by crested ridges. The foot 

 is thick and capable of con- 

 siderable extension. There 

 can be no doubt, in this case 

 at least, that the foot is the 

 boring instrument, for the 

 epidermis is conspicuous over 

 the front of the shell, where 

 worn off if the shell w^ere 



Wood Piddock 



it would be rapidly 

 used as a rasp. This 

 species is called the Wood Piddock, because it neglects 

 the rocks and bores only into submerged or floating 

 timber, preferring oak, pine, and birch, and evidently 

 not objecting to other vegetable substances, for it 

 has been found in the tarred hemp envelope of an 

 ocean cable. It penetrates only to a sufficient depth 

 (IJ inch) to bury itself, as shown in our figure. 



The remaining genus {Teiydo) of this sub-order 

 includes a few species of insignificant appearance, but 

 of sufficient power to have made them the despair for 

 centuries of all who owned wooden ships, timber-built 

 quays, piers, and stages in salt water. The people of 



