Praeger— Ow the Raised Beaches of N.E. Ireland. 51 



Trochus Itneatus, J). C. Abundant at the present time on the west 

 coast, as far north as Bundoran. Eare on the east coast, but 

 ranges north to Ballywalter in Co. Do-wn. Its presence in the 

 raised beach at Fort Stewart, on Lough Swilly, attests its further 

 former extension. 



Certain genera also exhibit, as a whole, striking fluctuations. 

 Trophon, so characteristic of glacial beds, is, with the exception of 

 T. muricatus in the Portrush bed, entirely absent in the estuarine 

 clays and raised beaches, re-appearing in the present north-eastern 

 seas with three species. Leda, another abundant glacial genus, with 

 three species in the local deposits of this age, is represented in the 

 estuarine clays and raised beaches by only a single valve of L. minuta 

 at Belfast, though two species inhabit our present waters. Astarte, 

 with four species in the glacial beds, is completely absent from the 

 estuarine clays and raised beaches, re-appearing with two species at 

 the present day. Cyprina is, very strangely, almost absent from the 

 glacial beds of the north-east; it is likewise extremely rare in the 

 estuarine clays and raised beaches, though now living in abundance. 

 Tapes, a genus of rather southern proclivities, is not represented in the 

 Ballyrudder beds, and but very sparingly in the boulder-clays. In 

 the estuarine clays and raised beaches all the British species are 

 widely diffused, often in very great abundance, while at the present 

 day one species, as already mentioned, has migrated completely from 

 the district, and another is almost extinct. Venus, another genus of 

 southern tendency, is unknown at Ballyrudder, and very sparsely 

 represented (two species only) in the boulder-clays. The estuarine 

 clays yield all the six local species, which have, if anything, in- 

 creased in numbers since that period. Montacuta, unknown in the 

 glacial beds, swarms in the estuarine clay, and is now extremely rare. 



"We have now traced, so far as is possible, the history and 

 character of the marine fauna of the north-eastern corner of Ireland. 

 We see that, following the Arctic climate that must have obtained 

 when the raised beach of Ballyrudder was laid down, somewhat 

 warmer seas existed during the boulder- clay period, inhabited by a 

 fauna still distinctly northern, but containing a few southern forms, 

 along with a diminishing number of Arctic species. It may be 

 remarked, in passing, that the character of this fauna closely corre- 

 sponds to that of the boulder-clay of KUl-o'-the-Grange, near Dublin, 

 recently described by Professor Sollas and the writer.' 



^ Irisli Naturalist, iv., p. 321, December, 1895. 



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