The taxonomic position of some cyphellaceous fungi has long been somewhat controversial, particularly for those occurring on mosses. The genus Mniopetalum was erected for those species of Leptoglossum which are associated with mosses and lack membrane pigments. Some like M. globisporum Donk lack lamellae while others like M. bryophilum (Pers.) Donk are distinctly agaricaceous when fully developed. In a more recent re-evaluation of species formerly placed in the genus Leptoglossum, Redhead (1984) reclassified about half the species in two major groupings, Arrhenia Fr. and Rimbachia Pat., Rimbachia replaced Mniopetalum Donk & Singer, a later congeneric name (Redhead 1984), and was extended to include Pleuromycenula Singer, while Rimbachia palmivora Singer was excluded as not being congeneric. Both genera would then be muscicolous, with lack of pigment being the most conspicuous feature separating Rimbachia from the pigmented Arrhenia. Singer (1986), however, does not accept Redhead's broader generic concept for the genus Rimbachia, stressing the inconsistencies associated with using habitat characters generically in this context. In two recent publications describing new species, Zang (1986) and Manimohan & Leelavathy (1988) have both followed Singer in retaining the genus Mniopetalum. The genus Mniopetalum is widespread, having been recorded from Europe, Asia, India, North and South America, and New Zealand. Cunningham (1953) recorded for New Zealand a species of the reduced genus Cyphella, C. muscigena Pers: Fr., which he believed to be the same as the European and North American species. This report was based on a collection with 1- and 2-spored basidia that compared well with the type of Singer's Mniopetalum bisporum (recombined as Rimbachia arachnoidea subsp. bispora (Singer) Redhead (Redhead 1984)). Another collection from New Zealand made by Horak was identified by Redhead (1984) as Mniopetalum megalosporum Singer (recombined as R. neckerae subsp. megalospora (Singer) Redhead). Both species are easily distinguishable, R. arachnoidea subsp. bispora having 2-spored basidia, smaller spores (7-9 x 5-6 µm), and a slightly wrinkled to venose hymenophore (Cunningham 1953; Singer 1966), whereas R. neckerae subsp. megalospora has 4-spored basidia, somewhat larger, more elongate spores (8.5-10 x 4-5.5 µm), and a smooth hymenophore (Singer 1969). Following is a description of a further species of Mniopetalum recently found in New Zealand on Hypnodendron colensoi (Hook.f. & W.Wilson) Mitten. This is quite distinct from the above species in having a distinctly venose hymenophore, small, spherical spores, and 4-spored basidia. This appears to be identical with Mniopetalum bryophilum (Pers.: Fr.) Donk.