Calycidium Stirt.
Thallus foliose, heteromerous, lobate, dorsiventral, to 4 cm diam. Lobes broad, rounded, flattened, margins entire, sinuous, often ± ascending. Photobiont green, Protococcaceae. Apothecia marginal on small lobules, mazaedium well-developed, surrounded by a narrow thalline margin. Asci cylindrical, thin-walled containing 8 irregularly arranged spores. Ascospores simple, spherical to irregularly ellipsoid, brown at maturity.
Calycidium is an endemic monotypic genus in the family Sphaerophoraceae [Murray T.R.S.N.Z. (Bot.) 88: 186-187 (1960); Sato Miscnea bryol. lichenol. Nichinan 4: 150-152 (1968)]; though Ohlsson ["A revision of the lichen genus Sphaerophorus". University microfilms, Xerox Company. Ann Arbor, Michigan. 270 pp. (1974)] in his unpublished revision of Sphaerophorus considers it more properly accommodated in a separate monogeneric family. The flattened, foliose thallus furnished with marginal apothecia distinguish it from the related genera Sphaerophorus and Thysanophoron.
