Page:The common shells of the sea-shore (IA commonshellsofse00wood 0).pdf/18



now pass to the Molluscs proper, and begin with those which have some resemblance in structure to the Ascidians.

The first group in our list is that which includes the various species of Pholas, the boring-shells which are so plentiful upon our rocky or chalky shores, and which are popularly known among fishermen as Piddocks. As the shell is better known than the animal, it will be first described.

At Plate I., fig. 12, is shown the common Piddock (Pholas dactylus), as it appears in the hole which it has excavated. The shell is beautifully white, and its whole surface is covered with deep grooves, sweeping in a bold hexagonal curve, and crossing each other so as to make the outer surface into a shelly rasp. The shells gape slightly above, and rather more below.