370 ON THE CORALS OF THE 
An Oolitic bivalve figured in the same work as Mytilus vicin- 
alis, very much resembles, both in size and form, save that it 
also is proportionally a massier shell, one of my smaller speci- 
mens. Some of the larger masses of the Helmsdale Isastrea 
are much fretted by this busy excavator. In one of the 
smaller fragments of coral on the table we find the fossil re- 
mains of three individual shells that had burrowed in it, and 
the cell of a fourth; and in the massive corallum beside it 
there are no fewer than four-and-twenty of these excavations 
now filled with grit, but doubtless once tenanted by a borer 
a-piece. If, as is probable, it was living at the time when the 
excavators were at work within it, and possessed, what is more 
questionable, the sense of feeling, it must have been wofully 
subject to stomach complaints and fits of griping in the bowels. 
Though these lithophagi of the Oolite occur chiefly in the 
corals of the period, they are not exclusively restricted to them. 
I have found them, though rarely, in Old Red flagstones of the 
conglomerate, and have ascertained that, had there been nat- 
uralists in those days to differ and dispute, the question might 
as certainly have been raised as now, whether the stone-boring 
shells made their way into the masses which they inhabited by 
mechanical means, or through the agency of some acidulous 
solvent. The corals, in their recent state, were of course cal- 
careous, and, in consequence, dissolvable by an acid; and the 
flagstones which the borers usually selected also contain a good 
deal of calcareous earth; but their prevailing material is so 
largely aluminous and quartzose, that it seems scarce likely 
that a mere solvent could have perforated them. 
I venture in conclusion, two general remarks. First, the 
corals of the Oolitic system in Scotland, massive in size, and 
occurring in some localities in very considerable abundance, 
resemble in these respects no recent corals of the higher lati- 
tudes. The corals of the higher latitudes are, we find, either 
