Harms, J., 1993. Check list of species (algae, invertebtates and vertebrates) found in the vicinity of the island of Helgoland (North Sea, German Bight) - a review of recent records. Helgoländer Meeresunters., 47: 1-34. Hayward, P.J., Wigham, G.D. & N. Yonow, 1990. Mollusca I: Polyplacophora, Scaphopoda, and Gastropoda. In: The Marine Fauna of the British Isles and North-West Europe. (ed. P.J. Hayward & J.S. Ryland). Clarendon Press, Oxford: 628-730. Seaward, D.R., 1990. Distribution of the marine molluscs of north west Europe. Nature Conservancy Council. Thompson, T.E., 1988. Molluscs: Benthic Opisthobranchs (Mollusca: Gastropoda). Synopses of the British fauna (NS), 8: 1-356. |