Abstract
A new species of Eunotia, E. pirla, is described from the epiphyton in Woolmer Pond, a strongly acid pool in Hampshire, England. The species is illustrated by drawings and light and scanning electron micrographs. E. pirla is considered to be conspecific with Eunotia species 19, described from two acid lakes in Michigan, U.S.A. (PIRLA 1986). Eunotia pirla is thought to be acidobiontic. The relative importance of possible factors influencing intraspecific morphological variation in the Woolmer Pond population is briefly discussed.