"If you examine these living shells," says Gosse, "you will see that the fore part, where the foot protrudes, is set with stony points arranged in transverse and longitudinal rows, the former being the result of elevated ridges, radiating from the hinge, the latter that of the edges of successive growths of the shell. These points have the most accurate resemblance to those set on a steel rasp in a blacksmith's shop. It is interesting to know that the shell is preserved from being itself prematurely worn away by the fact that it is composed of aragonite, a substance much harder than those rocks in which the Pholas burrows. The animal," Gosse adds, "turns in its burrow from side to side when at work, adhering to the interior by the foot, and therefore only partially rotating to and fro. The substance is abraded in the form of a fine powder, which is gradually ejected from the mouth of the hole by contraction of the bronchial syphon." The Pholades are met with on every sea shore, and are plentiful in the Channel; on the French coast they are called _Dails_, and sought for their fine flavour. As examples of the genus, we may quote _Pholas dadylus_ (Fig. 131); _Pholas candida_, found in the Channel and in the Atlantic Ocean, which lives buried in the mud or in decayed wood; _Pholas crispata_ (Fig. 132), also found in the Channel; _Pholas papyracea_ (Fig. 133); and _Pholas melanoura_ (Fig. 134). The bodies of many genera of Mollusca have the property of shining in the dark, but none emit a light more brilliant than that of the Pholades. Those who eat the Pholades in an uncooked state (which is by no means rare, for the flavour of the mollusc does not require the aid of cooking to render it palatable) would appear in the dark as if they had swallowed phosphorus; and the fisherman who, in a spirit of economy, supped on this mollusc in the dark, would give to his little ones the spectacle of a fire-eater on a small scale. [Illustration: Fig. 132. Pholas crispata (Linnæus).] The perforations produced in stone by the Pholades have become important evidence in a geological sense. In many countries there were evident signs of a considerable sinking of the earth. But in no place is the evidence of this so clear as in the monument of high antiquity on the Pozzuolan coast, known as the Temple of Serapis. [Illustration: Fig. 133. Pholas papyracea (Solander).] [Illustration: Fig. 134. Pholas melanoura (Sowerby).]