Cepaea nemoralis (Linnaeus, 1758) Grovesnail Sinistral

    Niagara Falls, Ontario, Canada (GPS: 43.108252N 079.065363W). Collected and photographed by Harold Lamb. Also see: Sinistral Cepaea nemoralis (Linnaeus, 1758).

Reversal of coil in Cepaea nemoralis (Linnaeus, 1758), the Grove Snail

by Harry G. Lee

     While the occurrence of reversed coiling of the Grove Snail is distinctly uncommon, a couple dozen finds, mostly single specimens, were reported over a century ago (Taylor, 1911: 321-322). Of greater interest are two reports of evanescent colonies of sinistral mutant individuals of this species in the U .K., to wit:

 (1) Taylor (1911: 322 <https://biodiversitylibrary.org/page/13263416> reported that Robert Welch recorded nearly 2000 sinistral specimens collected from Fenner Dunes, Bundoran, Ulster, N. Ireland, apparently Holocene subfossils. The specimen posted at http://jaxshells.org/cnem.htm was collected there by Peter Dance and is now at the Florida Museum of Natural History.

(2) Morrell (1979) reported in some detail finding up to thirteen living sinistral Cepaea nemoralis on single occasions in a small ruderal plot in Nottingham, U. K. He visited the area 18 times between 28 Sept., 1974 and 3 Oct., 1977 and only failed to find a living sinistral specimen twice. There were comparable numbers of dextrals in the area, but the two demes never occurred together. The colony disappeared during urban renewal, and just before then, his attempts in 1977 to transplant a dozen specimens to nearby Colwick Park apparently met with failure.

Morrell, R. W., 1979. A colony of sinistral Cepaea nemoralis (L.). Nottingham Naturalist 1: 21-24.

Taylor, J. W., 1894-1921. Monograph of the land and freshwater Mollusca of the British Isles. 3 vols. + 3 parts vol. 4. (unfinished). Taylor Bros., Leeds. <https://www.biodiversitylibrary.org/bibliography/13226#/summary>