In this paper the new species Myxarium crystallinum is described and its relationships with Tremella grilletii and Sebacina sphaerospora discussed. The two latter species are transferred to the genus Myxarium Wallr. An account of a third British gathering of Tremiscus helvelloides is given, together with a detailed review of its world-wide distribution, since it is one of the species included in the European Mapping Scheme for fungi.