Isolation of Intertidal Animals by Sea Barriers

Abstract

IN recent surveys of the Irish coast, we have established that several intertidal animals common in south-west Britain are not present in Ireland. The most notable absences are those of the barnacle, Balanus perforatus Bruguière, and the limpet, Patella intermedia Jeffreys (= P. depressa Pennant), both of which are found on the south coast of England west of the Isle of Wight, and off South Wales. Balanus perforatus extends only to the southern shores of Cardigan Bay¹, but Patella intermedia is found at least as far north as Holyhead; yet both are altogether absent from Ireland. Neither of these species has been suspected hitherto of being a recent immigrant to the British Isles; but of two other species which we failed to observe in Ireland, namely, the barnacle, Elminius modestus Darwin, and the bryozoan, Bugula neritina (L.), the former is known to be, and the latter thought to be, a ship-borne immigrant².