76 REPORT~1863. 
so often vex the surface. From this part of the sea-bed were often brought 
up loose boulders, stones, and pebbles, of various sizes; some of them were 
rounded, and others angular, but all more or less covered with Zoophytes. 
Some of the so-called corals attached to these stones were exceedingly fragile 
and delicate; and if the sea-bottom from which they were taken had been 
subject to the action of tides or currents, however feeble, the corals would 
assuredly be broken to pieces by the stones being rolled and coming into con- 
tact with each other. Even the underside of the smallest pebbles was usually 
encrusted with exquisitely fine living Polyzoa, which had not suffered any 
injury by lying loose on the ground. But, of course, the sea at such depths 
never stagnates ; it has a constant and free circulation throughout, and a 
ceaseless interchange of particles. In this region now live the species pre- 
viously known only in a fossil state and occurring in the middle and upper 
tertiary strata, and which might therefore be supposed to have become extinct 
on the advent of the glacial epoch. Considering the vast extent of sea-bottom 
which has never been touched by the dredge, the exceedingly limited space 
measured in square acres which can be explored by means of it, and the in- 
finite variety of ground comprised within any given area, I would suggest that 
great caution should be used, and further inquiries made, before the common 
expression is hazarded that certain species are now “ dying out,” whether 
slowly, gradually, or rapidly. I do not believe that such is the case. The 
fact of finding only dead shells in a particular spot is no proof that living 
ones cannot be met with in the same district. There may be, and often is, 
an accumulation of dead shells in one place, like bones in a grave-yard, in 
consequence of the shell-fish having deserted it for some reason with which 
we are not acquainted, while the living brood migrates or shifts its quarters. 
The proportion of dead to living specimens, even of common species which 
are not supposed to be “dying out,” is often remarkable. Among many 
hundred single valves of Lima subauriculata which were this year dredged 
in Shetland, there was only one live specimen. Scalaria Turtoni has lately been 
dredged in considerable numbers off the Yorkshire coast ; but all the speci- 
mens were dead. No one has yet found a live Adeorbis subcarinatus, although 
it is by no means uncommon in the greater part of the European seas. The 
late Professor Forbes described, in his admirable contribution to the Memoirs 
of the Geological Survey for 1846, what he called “a boreal outlier,” or 
isolated assemblage of northern shells, which he found while dredging with 
Mr. M‘Andrew in the deeps of Loch Fyne. He said, “The dead Mollusks 
taken were Abra Boysii, a species of similar range with Nucula nucleus ; 
Cardium Lovéni, a Scandinavian species; and Pecten Danicus, a Norwegian 
species found only in the British seas, in the lochs of the Clyde, and then 
rarely alive, though dead shells are abundant, as if the species thus isolated 
were now dying out.” Having had peculiar opportunities of studying the 
geographical distribution of the British Mollusca, I may mention that the 
species first named (Abra Boysii, or Scrobicularia alba) inhabits the Mediter- 
ranean, as well as the western coast of France ; Cardium Lovéni, or C. Sueci- 
cum, is identical with C. minimum of Philippi, and is also a Mediterranean 
species; and Pecten Danicus (or P. septemradiatus, alias P. adspersus) has 
an equally southern range, although it is known in France and Italy by 
names differing from those which have been given to the same species in the 
north. P. septemradiatus is taken alive in considerable numbers by the fisher- 
men in Loch Fyne, during the herring-season. Mr. Barlee obtained from them, 
ten years ago, two or three hundred perfect specimens during a short stay at 
Inyerary ; the principal shell-dealers continually receive supplies of this 
