Nomenclature of the British Littorinidæ

Abstract

THE currently accepted classification of the British Littorinidæ (= Lacunidæ) is that of Winckworth¹. In his earlier publication² on the nomenclature of this group, Winckworth assigns the species formerly included under Littorina, on the basis of differences in the methods of reproduction, to four genera, thus: (1) L. littorea (L.) to Littorina Ferrusac, (2) L. saxatilis (Olivi) to Littorivaga Dall, (3) L. neritoides (L.) to Melarhaphe Menke and (4) L. obtusata (L.), L. æstuarii (Jeffreys) and L. littoralis (L.) to Neritoides Brown (the occurrence of obtusata in Great Britain being, however, thought doubtful). "It has long been known that L. littorea has pelagic egg-capsules and passes through a free Veliger stage, while L. rudis is viviparous and L. littoralis, like the species of Lacuna, deposits eggs in oothecæ on the seaweeds." To the objection that these differences are ecological and should have no place in a classification based on morphology, Winckworth‘s reply was: "The closest groups are Littorina and Neritoides and to my mind the distinction between a Molluse with a free Veliger stage and one that does not pass through this stage still remains of generic importance, while in other groups the genera could be separated on anatomical and conchological distinctions. Those who do not see with me in this may regard the names as of a sub-generic rank." Accordingly, in his later publication¹, he treats Littorivaga, Melarhaphe and Neritoides as sub-genera of Littorina, without any further discussion.