13 
(c) Chocolate brown clay, with boulders, some scratched 
and occasionally slightly bedded, forming the 
general base of both eastern and western cliffs 
of the isthmus. Formerly well exposed where 
the new sea wall and boatstairs are near Tygwyn, 
Llandudno. At this spot fragments occurred of 
Tellina solidula, Mactra solida, Astarte arctica, 
Cardium edule. 
The same bed appears at Colwyn ballast cut- 
ting under sandy clay and old beach shingle, with 
fragments of the same species and of Saxicava. 
(d) A very similar bed of lighter coloured reddish clay 
with rounded and angular stones, in the west 
cliff, and generally over the isthmus. 
In the cliffs occurred fragments of Mya trun- 
catia, Tellina solidula, Mactra , Cardium 
edule, Mytilus edulis, and Buccinum undatum. 
The same bed and like fragments of shells are 
seen at 70 — 80 feet above the sea near the bath 
house, and according to Mr. Maw, as high as 170 
feet up the Gwydfyd Valley. 
Mr. Binney had found Turritella terebra, and 
had pointed out the similarity of those beds 
with those at Blackpool. Mr. Maw had identified 
the boulder clay also in a terrace about 170 feet 
high on the south. 
The occurrence of travelled boulders indicated 
the former existence of the bed at higher levels; 
thus a mass of greenstone had occurred above 
Gwydfyd farm at 380 feet elevation. 
These boulder clays, the author supposes to have been 
deposited at the close of the glacial epoch, and to be the 
result of redistribution of older beds on the coast of a rising- 
land, mixed with old drift and land drift, swept down by 
the glaciers of Snowdonia, in whose recesses the astarte and 
other shells occur on ancient beaches. 
