194 
THE RHiETiC ROCKS OP NOTTINGHAMSHIRE. 
We cannot, however, affirm or believe that in England we possess 
even a imderate representative of the Mid-European Rhastic formation, 
for nowhere in Britain do the Rhaetics exceed 100 feet in thickness 
(including the Tea-green marls at the base). In the Austrian Alps 
they are between 3,000 and 4,000 feet, and in the Rhastian Alps nearly 
the same, so that our most typical sections (long as the time may be they 
have taken to be deposited) are poor representatives of the spoils of that 
sea which occupied a large European area at a time between the close 
of the Trias and the commencement of the Jurassic epoch, thus linking 
together those two great formations. 
Though we may justly regard the Triassic epoch over much of what 
was then Europe as a terrestrial one, and admit with Ramsay that the 
New Red sandstones and marls were accumulated in inland seas or 
salt lakes surrounded by masses of land, we must recognise the very 
marked and general change that commenced with the Rhaetic stage, a 
change brought about by gradual depression of these lakes or lagoons 
into a sea ; for the forms of the Rhaetic are all marine ; and in con¬ 
nection with this also we note the parallelism and conformity of the 
Rhaetic with the marine Liassic deposits not only through England, 
but also over nearly all Western Europe. 
The peculiar/acfes of the Mollusca of the British Rhaetics attests their 
abnormal marine condition, and comparison witli the fossil remains of 
the Italian and Austrian Rhaetian beds shows the shallow, marginal, 
and brackish nature of the scanty British deposits, and the poverty of 
the species, besides the dwarfed and stunted aspect of the forms com¬ 
pared with those of the normal deposits of Lombardy. Thus also we 
can understand the small vertical development of the Rhaetic strata 
in this country. 
In Britain the Rhaetic series, though so thin, forms a clearly defined 
and continuous line from Redcar and the bold headlands on the York¬ 
shire coast to the Cliffs of Dorsetshire, exhibiting to us on the way, 
those magnificent sections in the valley of the Severn at Watchet, 
Penarth, Westbury, and Aust Cliff, also at Axmouth on the English 
Channel, while the coasts of Londonderry and Antrim give unequivocal 
proofs of these rocks having once occupied an immense area now 
covered by the waters of the North Atlantic, or buried beneath the 
ancient lava flows and basaltic columns that form the coast line of the 
Great Causeway.* 
Rhaetic rocks were first noticed in the Nottinghamshire district 
about fifteen years ago by Mr. F. M. Burton, F.G.S., near Gains¬ 
borough,! just outside the county boundary, and were subsequently 
* “The Rhaetic or Avicula contorta beds at Garden Cliff, Westbury-on- 
Severn,” by R. Etheridge, F.R.S.—Proc. Cotteswold Naturalists’ Field Club, 1864. 
“ On the Physical Structure and Organic Remains of the Penarth Beds of 
Penarth and Lavernock,’’ by R. Etheridge, F.R.S.—Cardiff Naturalists’ Society, 
1871. 
+ “ Q. J. G. S.,” 1867, p. 315. 
