On Some Small Ianthina Janthina (L.) Stranded on the Isles of Scilly, 1957

Extract

In an earlier paper (Wilson & Wilson, 1956) there was described a large-scale stranding, on the shores of Cornwall and Devon in 1954, of the pelagic gastropod Ianthina janthina (L.). Most of the shells then collected were broken, but thirty-six were entire and measurements of these showed that, in spite of considerable variation in the proportion of width to height, the width is proportionately greater in young than in old shells. None of the 1954 shells was less than half an inch high, the majority being considerably higher. Two shells stranded at Sennen several years before, and the figure of one in a paper by Fowler (1947, as I. planispirata Adams & Reeve) were the only specimens less than half-an-inch high available for comparison with the larger ones. The measurements of these agreed with the general conclusion that as the shell grows it becomes proportionately less wide. In the past these variations in shell shape have been responsible for the erection of a number of different species. In order to establish the conclusion firmly it was desirable to examine a collection of young shells.

On 31 March 1957 Mrs M. Hicks wrote from St Agnes, Isles of Scilly, to say that on that day her husband had found eight small Ianthina, six of which had stranded alive on the afternoon's tide, the other two, one of them alive, earlier. Subsequently more were collected. On 8 April Miss Deborah Hicks (age 9) picked up about 130, some of them living, some apparently not.