40 Proceedings of the Royal Physical Society. 
are still covered with their epidermis. In no case have I 
found two valves united. Several of the shells are perforated 
by the whelh and the sponge Cliona. Some of the zoo- 
phytes, Polyzoa, are attached to broken shells ; other mark- 
ings are also seen on them like those on our present living 
shells. Many of the shell fragments have their broken edges 
rounded ; others, again, are as sharp as if only just broken. 
This latter circumstance, I know, causes surprise, and often 
difficulty to many. All this will vanish if those doubting 
would collect shells on the present sea-shores ; they will find 
that rounded and sharp fragments occur together, agreeing in 
every respect with those found in the Boulder-clay. 
Most of the organisms of the Boulder-clay are still to be 
found alive on our own shores, as may be seen by the 
accompanying lists, — two only of the shells, viz., Astarte 
arctica and Tellina proxima, being Scandinavian ; one alone, 
viz., Trophon scalariforme, being Arctic. The mode of 
transport of the materials of the Boulder- clay, in all pro- 
bability, has been ice, either by glaciers or icebergs. As I 
wish only to introduce the organisms of its own age, I must 
leave this part of the subject to others. 
I think it right to state that the whole of the shells have 
been examined and named for me by J. Gwyn Jeffreys, 
Esq., the sponge Geodia by Dr Bowerbank, both excellent 
authorities ; therefore the list may be safely accepted as 
correct. For the remainder I am answerable. 
The greater part of these organisms have been collected 
by myself, assisted by my sons. All the species got by them 
I have also found, and in no case have I admitted into the 
list any specimen found in a dotchtful position, alw^ays keeping 
in view the human skull and rybat mentioned by the late 
lamented Hugh Miller. Had I been inclined to do so, I 
might have noticed the skull of an Arvicola from the Wick 
cliffs, found in a much less doubtful position than the human 
one. I have taken only those dug out of the solid clay. The 
whole of the specimens are in my possession, and I shall be 
happy to show them to any one working in this field of 
research. 
