253 
interval sufficiently long, and the geographical and climatal 
changes involved must have been sufficiently great to have 
allowed the arctic forms to migrate north, and southern life to 
take their place ; but what the shore in earlier Glacial times 
contained we cannot tell. It has not risen again, and lies 
still deep below the sea. 
In these Moel Tryfaen beds some fifty-four species have been 
found ; of these, thirty-seven are still living in the neighbouring 
sea.* Now, we do not get gravel and sand continuous from this 
height down to the level of the shore. But on the northern 
shores of Cardigan Bay, in promontory of Lleyn and Anglesea, 
Ramsay records them. Near Macclesfield nearly the same 
group of shells occurs. f A happy combination of conditions 
preserved these two records of the great submergence. Be- 
tween these two points there is no evidence of any similar beds 
so high ; but at a lower level, gravel, sand, and loam occur at 
various places along the North Wales coast, and with numerous 
shells up to between 200 and 300 feet. These seem, from the 
cumulative evidence to be given hereafter, to belong to a later 
period of the same great submergence, and as the land had not 
risen high enough to reintroduce glaciers upon the heights, so 
there was no recurrence of colder forms along the shore ; but 
the migration of southern forms towards the north had still 
gone on, and so we find but two or three arctic types among 
the shells. 
For instance, in the Yale of Clwyd, at various points we find 
a mass of sand and gravel associated with red clays with boul- 
ders, some round, some broken, some showing glacial striae, 
and some not. The shells occur both in the sand and in the 
clay — more commonly in the sand. The sand and gravel are 
oftener in the middle, with clay above and below ; but some- 
times there is hardly any clay, sometimes no sand. 
The shells are almost always fragmentary, and all but two 
are common on the coast but six miles to the north. 
They are : — J 
Dentalium abyssorum or tarentinum. 
Littorina littorea. 
* More recently, Mr. Gwyn Jeffreys has given a list of the Moel 
Tryfaen fossils, corrected up to the latest date (Quart. Journ. Gcol. Soc., 
June 9, 1880). He says that there are sixty species, besides three distinct 
varieties, of which eleven are arctic, or northern, and the rest still live in 
Carnarvon Bay. 
t Darbishire, Geol. Mag., vol. ii., 1865, p. 293. 
+ Most of them were determined for me by Searles Wood, Jun. 
