104 CHAS. L. WALTON. 



resulting in appreciable local modifications of some of the elements o£ 

 the Fauna. 



The portion of the Bay in which the above-mentioned conditions are 

 most typically developed lies between Portmadoc to the north and 

 Cardigan to the south. Aberystwyth lies practically in the centre, and 

 as the f aunistic work has been carried out from that point, and since time, 

 distance, and accessibility have, as usual, played their parts, the coast 

 in the vicinity of Aberystwyth has been much more thoroughly examined 

 than the rest. Practically no records have been made south of the Teifi, 

 and but few above Portmadoc. It is fortunate that the region most 

 readily accessible includes all the types of coast. It will be seen that 

 there are three principal types of shore, and that these are subject in a 

 marked degree to several important factors. (1) Wave disturbance 

 (surf action). (2) Erosion by detritus and shingle. (3) Muddy fresh 

 water. 



These adverse conditions are reflected in the comparative poverty of the 

 Fauna. In connection with the above factors, peculiarities have been 

 observed in the distribution of certain groups, notably some of the 

 Mollusca, and these are dealt with separately. It is hoped, later, to 

 study the Fauna of the Bay below low-water mark and a number of 

 records are already available : the comparison should prove of interest. 

 It follows from what has been said above, that the shore Fauna will 

 consist chiefly of the more hardy species, supplemented by some others 

 that may survive in the more sheltered spots. The nomenclature adopted 

 is mainly that of the " Plymouth Marine Invertebrate Fauna," 1904. 



It will be observed that the Echinoderms and Ascidians are very 

 poorly represented. The Crustacea and fishes have been limited as far 

 as possible to shore forms, but a hard-and-fast line cannot be drawn. The 

 worms have not been at all adequately examined and require the attention 

 of a specialist. The following abbreviations are used to denote the 

 observers responsible for the various records : — 



H. J. F. = Prof. H. J. Fleure, D.Sc. 

 F. S.W. = F.S.Wright. 

 C. L. W. = C. L. Walton. 



