DEPOSITS OF SCOTLAND, 397 
nomena the most decidedly boreal of the group. Every rock- 
surface on which it rests is grooved and striated; almost 
every softer pebble which it encloses is scratched and furrowed, 
usually in the line of its longer axis; all its larger shells exist 
as broken fragments, often rounded as if by attrition, and bear- 
ing in their lines and scratches marks of the same agents that 
dressed the rocks and scored the pebbles; nay, the very sub- 
stance and color of its prevailing clays show that it is mainly 
composed of the dressings of the rocks on which it rests,— all 
giving evidence, apparently, of a time when our half-foundered 
country sat from eight hundred to a thousand feet lower in the 
water than it does now, and vast packs of grinding: icebergs 
went careering over what are now its lower hills and its higher 
table-lands. 
The Clyde beds and their contents belong apparently to a 
still later time. Their largest shells are usually in a state of 
great entireness and fine keeping. I had the pleasure of laying 
open, two years ago, at Fairlie, on-the Ayrshire coast, a virgin 
deposit unknown before, in which I found continuous scalps of 
Pecten Islandicus still occupying the place in which they had 
lived and died, and with their upper valves covered with large 
balan, such as we now dredge up from the outer limits of the 
laminarian zone, and all fresh and unbroken. Huge Panopea 
were there sticking fast in an unctuous clay, with their open 
siphuncular ends turned upwards; and entire specimens of 
Cyprina Islandicus and Modiola Modiolus, with their valves 
still connected by the sorely decayed ligament. Tellina prox- 
ima was abundant, but reduced in size to little more than half 
the Gamrie dimensions. I found Astarte elliptica the prevail- 
ing Astarte; and groups of younger Cyprina huddled together 
in the character — which they do not now assume on our coasts 
—of gregarious shells. No crushing iceberg had passed over 
this deposit: a grooved and polished rock of Old Red Sandstone 
34 
