BIVALVE MOLLUSCA. 331 
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. 
The perforations produced in stone by the Pholads have become 
important evidence in a geological point of view. In many countries 
there are evident signs of a considerable past sinking and then up- 
heaval of the earth. But in no place is the evidence of this clearer 
than in a monument of high antiquity on the Pozzuolan coast, known 
as the Temple of Serapis (PLATE XL.). 
In speaking of the culture of oysters by the Romans we shall have 
occasion to mention the disappearance of the Lucrine Lake, and its 
replacement by an enormous mountain, the Monte Nuovo. Now, 
Pozzuolo is situated at the foot of Monte Nuovo. We need not add 
that the whole neighbourhood is volcanic. Pozzuolo touches on the 
Solfaterra, on the Lake Avernus, and is not far from Vesuvius; and in 
the bay is the monument of other days, erroneously called the Temple 
of Serapis. In reality it was most probably a thermal establishment, 
established for its mineral waters, although the world has now agreed 
to call it a temple. 
However that may be, the building has been nearly levelled by the 
hand of Time, aided by the hand of man; and the ruins now consist of 
three magnificent marble columns of about forty feet high. But the 
curious and important fact is, that these three columns, at about ten 
feet above the surface, are riddled with holes, and full of cavities bored 
deeply into the marble, and these borings occupy the space of about 
three feet on each column. The cause of these perforations is no longer 
doubtful. In some of the cavities the shell of the operator is still 
found, and it seems settled among naturalists that it belongs to a 
species of Pholas, although M. Pouchet, a naturalist of Rouen, denies 
this. “As far,” he says, ‘(as I have been able to judge from the 
fragment which I extracted from this temple, which is destitute of 
the hinge, it is infinitely more probable that this mollusc is a species 
of the genus Coralliophaga.” In spite, however, of M. Pouchet’s 
scepticism, the mass of evidence is opposed to his theory. 
There are two modes of explaining the fact to which we have called 
attention. To enable the stone-boring molluscs, which live only in 
the sea, to excavate this marble, the temple and columns must have 
been buried several fathoms deep in sea-water. It is only in these 
conditions that the borers could have made burrows into, and laboured 
at their ease, in the marble columns. 
But since the same traces of perforation are now visible ten feet 
