Abstract
During a three year study of the larval trematodes of Llangorse Lake, South Wales, twenty-one species of cercariae have been encountered. The present paper deals with four cercariae of the Gymnocephalous group. Two new species of Agilis cercariae are described in detail; Cercaria Sphaeridiotrema globulus is recorded from Britain for the first time and the occurrence of Cercaria lophocerca noted