Studies on the Biology of British Limpets.

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Abstract
Summary.: (1) The limpets of Cardigan Bay have been studied to provide records additional to those of Eslick (1940) for the Isle of Man and those of Fischer‐Piette (1935, 1938) for the Channel coasts, and to place the recognition of the three species on a clearer basis.(2) The nomenclature of the British species of Patella is discussed, and it is decided to adhere, in the present study, to the system adopted by the Plymouth Marine Fauna (1931), and by Winckworth (1932), i. e. Patella vulgata L. Patella depressa Pennant. Patella athletica Bean.This is related to the systems adopted by other workers.(3) From a detailed study of 400 limpets in the laboratory and an examination of several hundred specimens in the field, descriptions of the various conchological and anatomical characters have been made. The results are compared with those of Fischer‐Piette (1935, 1938) and of Eslick (1940), and it is established that the three species are quite distinct in Cardigan Bay. A key is suggested for identification, based on external characters.(4) The horizontal and vertical distributions between tide‐marks of the three species are described and are found to be quite distinct, although some overlapping occurs as among other intertidal forms.(5) It is shown that while Patella vulgata and P. athletica probably occur all round the British Isles, there is no evidence that P. depressa occurs north of the Irish Sea and Bristol Channel. The statement of Fischer‐Piette (1935) that the three species merge in certain areas (e. g. the Isle of Wight) needs re‐investigation and an extensive and detailed analysis of the limpet populations at such localities. The resemblance between the dentition of P. vulgata and P. depressa is discussed, and the possibility of hybridization, in localities where both occur freely, is considered. It is shown that the similarity of the pluricuspids is much more marked in an area where both species are common (Cardigan Bay) than where P. vulgata only occurs (Isle of Man).Since the completion of the above work, I have examined several shells collected by Professor T. A. Stephenson at Salcombe, Looe, Bedruthan Steps, Watchet, Easdale, Staffa, Tantallan, and Charlestown. They are easily separated into the three distinct types here described, and differ in no significant way from the shells collected in Cardigan Bay.

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