2 TERETE SPECIES OF GRACILARIA AND GRACILARIOPSIS (GRACILARIALES, RHODOPHYTA) IN BRITAIN

Two terete species of gracilarioid algae are described for the British Isles. Gracilaria gracilis comb. nov. and Gracilariopsis longissima comb. nov. (Gracilariopsis verrucosa nom. rej. prop.) are superficially similar species long confused under the name Gracilaria verrucosa (Hudson) Papenfuss (= G. confervoides (Stackhouse) Greville), until recently regarded as the type species of the genus Gracilaria Greville. They occur regularly on southern British coasts, often in the same locality, both inter- and subtidally. Gracilariopsis longissima is also recorded for the first time from France and Spain. A lectotype is selected for Gracilaria gracilis, Gracilariopsis longissima is neotypified, and new descriptions are given, including field characters and new details of vegetative and cystocarp structure obtained by sectioning in standard planes, using metachromatic dyes. The British record for Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik is not confirmed. Revision of those definitions of agar which include an incorrect specific name is recommended.