77 
That at some time they have been submerged by the waters 
of the ocean seems indubitable, for the cavities in which the 
lithophagse burrowed are still fresh, and tell of other aspects 
and other times.” 
At page 77, the author again says, in describing the 
country: — “We will not pretend to trace it through the 
many changes, or attempt to describe it when the breakers 
laved the rock of Stainton and the lithophagse burrowed in 
those immense blocks which are still left to attest the fact.” 
The Carboniferous Limestone alluded to by Mr. Jopling in 
Furness, Lancashire, is only a few miles from the shore of 
Morecambe Bay, and in the localities alluded to by him will 
be at an altitude of about two hundred feet above the 
present sea-level. 
He was not competent to form an opinion as to the holes 
and hollows in rocks seen and described by the above- 
named observers, but probably such, phenomena, even if 
clearly proved to have been the work of a mollusk, should 
be classed under three heads, namely: — 1st, those in the 
bare rock; 2nd, those covered by sward and vegetable 
mould; and, 3rd, those covered by till or other drift. In 
all these cases the shape of the original hole or hollow made 
by the Pholas would no doubt be considerably modified by 
the different causes to which they had been subjected. 
In the first case, they would be subject to the action of the 
carbonic acid in the rain-water, and aqueous and atmo- 
spheric agencies. In the second case, not only to those 
effects, but to the decomposing action of organic acids 
arising from the decaying vegetable matter. And, in the 
last instance, to long-continued aqueous and atmospheric 
agencies before the rock was covered up by the drift 
deposits. 
Great care ought to be taken before a hole in a rock 
should be attributed to a mollusk, especially in limestones, 
which so frequently exhibit on the surface markings of 
nearly every variety of form. 
