On dead Beilschmiedia tawa, Wellington, Lake Papaitonga, 8.IX.l953, G. H. Cunningham (HOLOTYPE, PDD12619).

Fructifications soft-waxy to fleshy, resupinate, thin, effused, indeterminate, originating as circular patches, coalescing to form irregular areas to 5 cm in longest dimension, white to sordid white when fresh, drying to a conspicuous white crust; margins concolorous, adnate. In section 75-200 µm thick, consisting of basal layer and hymenium; granular material abundant throughout fructification. Basal layer well defined, composed of distinct, interwoven, septate hyphae 2-3.5 µm diam., lying parallel with substratum, clamp connections absent. Hymenium composed of dikaryophyses and basidia; dikaryophyses arising from basal hyphae or fertile hyphae, simple or sparingly branched, irregular, often irregularly subclavate and to 7 µm diam., septate; probasidia clavate, typically distinctly stalked, proliferating through or near basal clamp connections, 17.5-24.7-(27) x 7.8-11.7 µm, becoming longitudinally cruciate-septate, longitudinal septa often diverging basally to delimit inflated apical portion from stalk; sterigmata cylindrical, to 30 x 2.5-3 µm. Basidiospores cylindrical, curved-cylindrical, or occasionally ovate and flattened on one side, hyaline, apiculate, 11-14.3 x 4.8-6.8 µm. Germination by repetition.

Dead angiosperm wood.

Fructificationes molliter ceraceae ad carnatas, resupinatae, tenues, albae ad sordide albas; ordo basalis factus ex hyphis distinctis, septatis, enodosis. Dikaryophyses simplices vel raro ramosae ad apicem, irregulares, septatae; probasidia clavata, stipulata, 17.5-24.7-(27) x 7.8-11.7 µm, per longitudinem cruciata-septata; sterigmata cylindrica, ad 30 x 2.5-3 µm. Basidiosporae cylindricae, curvo-cylindricae vel interdum ovatae, 11-14.3 x 4.8-6.8 µm. Germinantes per repetitionem. Habitat in mortua Beilschmiedia tawa.

The absence of both cystidia and gloeocystidia indicate that this species belongs in sect. Sebacina.
The morphology of the basidia varies within the single collection. The majority possesses stalks formed by divergence of the longitudinal septa in basal regions, but a number of basidia lacking stalks are also present. An interesting feature of S. tawa is the absence of clamp connections on the internal hyphae except at the base of the basidia. S. tawa does not appear to be closely related to any of the species included in Exidiopsis by Wells (1961). The species is characterised by the simply septate internal hyphae, typically stalked basidia with basal clamp connections, and cylindrical to curved-cylindrical spores.

Typus Wellington Province, Lake Papaitonga, 8.IX.l953, G. H. Cunningham, PDD 12619.