Shell morphology and allozyme patterns of 17 enzymes are analysed within the isolated population ofL. saxatilisOlivi (1792) from Venice, the type locality of the species. The shell morphology is compared to three differentL. saxatilisphenotypes from Sweden, and showed to be similar to the brackish water‘tenebrosa’type. The Venice population is genetically more distant from British and Swedish populations than are the latter from each other. Less variability (heterozygosity) within the Venice compared to the Atlantic populations is probably a consequence of random genetic drift during a period of small population size.The nomenclature ofL. saxatilisin the Atlantic is discussed and it is suggested that until the exact taxonomic relationship between the Mediterranean and the Atlantic populations has been confirmed by, for example, cross‐breeding experiments, the name‘saxatilis’should be kept for the non‐Venetian populations (described by Maton (1797) under the n