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The Shore Fauna of Cardigan Bay. 



By 



Chas. L. Walton, 



Universittj College of JVales, Abeiijstwyfh. 



€aedigan Bay occupies a considerable portion of the west coast of 

 Wales. It is bounded on the north by the southern shores of Carnarvon- 

 shire ; its central portion comprises the entire coast-lines of Merioneth 

 and Cardigan, and its southern limit is the north coast of Pembrokeshire. 

 The total length of coast-line between Braich-y-pwll in Carnarvon, and 

 Strumble Head in Pembrokeshire, is about 140 miles, and in addition 

 there are considerable estuarine areas. The entire Bay is shallow ; for the 

 most part four to ten fathoms inshore, and ten to sixteen about the centre. 

 It is considered probable that the Bay was temporarily transformed 

 into low-lying land by accumulations of boulder clay diu'ing the Ice Age. 

 Wave action has subsequently completed the erosive removal of that 

 land area, with the exception of a few patches on the present coast-line 

 and certain causeways or sarns. Portions of the sea-floor probably still 

 retain some remains of this drift, and owing to the shallowness, tidal cur- 

 rents and wave disturbance speedily cause the waters of the Bay to become 

 opaque. The prevailing winds are, as usual, south-westerly, and heavy 

 surf is frequent about the central shore-line. This surf action is accen- 

 tuated by the large amount of shingle derived from the boulder clay. 

 The action of the prevailing winds and set of drifts in the Bay results in the 

 constant movement northwards along the shores of a very considerable 

 cpaantity of this residual drift material. Where checked by shore contour 

 or river current this drift accumulates to form storm-beaches, which 

 have eventually deflected certain rivers and streams to the northward, 

 as in the case of the Ystwyth at Aberystwyth, the Clarach stream a 

 little further to the north, and the Leri at Borth. Other large accumula- 

 tions have assisted in the raising of the sarns or " causeways," extensive 

 shallow regions, several of which run out in its northern half into the 

 Bay for a considerable distance. One of these, the Sarn Badrig. dries at 

 low-water spring-tides, nearly 14 miles from land. 



