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 c omb. nov. (Gracilariopsis verrucosa nom. rej. prop.) are superficially similar species long confused under the name Gracilaria verrucosa (Hu dson) Papenfuss (= G. confervoides (Stackhouse) Greville), until recen tly regarded as the type species of the genus Gracilaria Greville. The y occur regularly on southern British coasts, often in the same locali ty, both inter- and subtidally. Gracilariopsis longissima is also reco rded for the first time from France and Spain. A lectotype is selected for Gracilaria gracilis, Gracilariopsis longissima is neotypified, an d new descriptions are given, including field characters and new detai ls of vegetative and cystocarp structure obtained by sectioning in sta ndard planes, using metachromatic dyes. The British record for Gracila riopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik is not confirme d. Revision of those definitions of agar which include an incorrect sp ecific name is recommended.