File:The Quarterly journal of the Geological Society of London (13935378792).jpg

1866.. JAMIESON CAITHNESS. 267
Fig. 5. — Oil the Thurso Water, near Thurso.
Sfcream. Farmhouse. W.
The high, banks on both sides of the stream consist of unstrafcified pebbly clay
or gritty mud with a few traces of broken shells.
from rocks in some part of the county, with the exception of one of
granite near Castletown, which he thought was different from any
of the Caithness granites, and had probably come from Sutherland,
where a similar quality of rock is known to occur.
4. State of the Shells. — The shells, as a rule, occur in broken frag-
ments. The most common kinds are the Oyprina Islandica, Turri-
tella ungulina, Astarte horealis, A. elliptica, Tellina calcaria, and T.
Balthica. Although broken pieces are the rule, yet exceptions
sometimes occur. Thus, during the search that I myself made, I
found one entire valve of Astarte horealis, another of A. elliptica,
and two small ones of A. compressa, likewise a specimen of Natica
nitida and another of JSf. Islandica, both almost perfect. And in
the collections of Mr. Joseph Anderson and Mr. Eobert Dick I saw
several entire single valves of Astarte and Leda, on which there were
occasionally small portions of the epidermis or skin remaining, also
entire specimens of Mangelia and Nassa. Mr. Peach has even got
a specimen of Anomia with both valves complete, in a fine state of
preservation, and this was in the drift containing the usual assem-
blage of ice-worn stones and broken shells, the only instance of an
entire bivalve that I have heard of. The Tur^itella, which is one of
the most common of all the species, although always more or less
imperfect, yet frequently occurs in large pieces, some of them not
far from being entire. I nowhere observed any instance of the shells
being found in an undisturbed condition, nor could I hear of any
such having been found ; there seems to be no such thing as a bed
of laminated silt with shells in situ. Even the Foraminifera, when
seen through the microscope have a rubbed, worn appearance. No
clay suitable for the manufacture of bricks and tiles or drain -pipes
has been got in Caithnes, it is all too sandy and full of stones. The
laminated brick-clays are, in short, entirely absent.
Many of the shell-fragments show marks of glacial action. It is
generally on the stouter pieces of Cyprina and Astarte that these are
to be seen, but I found some fragments of Tellina calcaria distinctly
marked. Now this is rather a delicate fragile shell, and the fact of
its being so marked and yet not crushed to powder, shows how gentle,
in some cases, the action must have been that imprinted these
markings. Where the shell-fragments are of an elongated form, the
scratches run lengthways along them, just as they do on the pebbles.
I have one piece of shell, which T picked up myself, not quite an
inch long, most beautifully marked with a multitude of fine parallel
scratches as if done by the point of a needle, and quite polished even