Johnston (1998) described Pirottaea falcata from the leaf tomentum of Asteraceae in New Zealand (from species of both Olearia and Celmisia). The descriptions and illustrations of Johnston (1998; Fig.1) and Sydow (1924; Fig. 2) clearly represent the same fungus, characterised by small apothecia witha short, stipe-like base, and sickle-shaped setae, embedded within the leaf tomentum on the undersides of leaves of Asteraceae. The ascospore sizes given in Sydow's (1924) description are slightly longer and narrower than those given by Johnston (1998). This may reflect differences in mounting media used in the studies, or could reflect differences in the level of maturity of the material examined. Johnston (1988) saw ascospores only within the asci, possibly indicating that the material examined was slightly immature. The type specimen of Chaetoscypha nidulans was not able to be examined. Although listed in the PDD herbarium catalogue, the type specimen of C.nidulans was noted as missing from PDD by McKenzie et al. (1992). Duplicates of this specimen are not present in either of the European herbaria with major Sydow holdings, S and W.Sydow (1924) considered that C. nidulans could not be placed in the genus Pirottaea Sacc. because of what he described as a prosenchymatous excipulum, in contrast to the parenchymatous excipulum that he considered characteristic ofPirottaea. The illustrations of Johnston (1998; Fig.1) show that the excipular structure in fact appears to match Pirottaea well, although the excipulum is extremely reduced (in places the ectal excipular layer being a single cell wide), and there is a poorly developed outer layer comprising meandering hyphae across the surface of the receptacle. The dark,thick-walled setae are quite unlike the hair-like elements characteristic of Hyaloscyphaceae. Chaetoscypha was not treated by Nannfeldt (1932,1985) in his detailed treatments of Pirottaea and related genera.

Sydow (1924) described the genus Chaetoscypha, with the New Zealand fungus C. nidulans Syd. as the type species. No further species have been added to the genus, and its position remains uncertain. Kirk et al. (2001) considered that it may be a synonym ofLachnum Retz., possibly following Sydow's suggestion that this species belonged in his higher taxonomic group "Dasyscyphearum", a group similar in concept to the modern Hyaloscyphaceae. Chaetoscypha nidulans was described from a single collection made from fallen leaves of the alpine tree daisyOlearia colensoi. C. nidulans develops within the tomentum on the lower leaf surface, a feature well developed on O. colensoi and many other New Zealand alpine Asteraceae.

TAXONOMIC TREATMENTPirottaea nidulans (Syd.) P.R.Johnst., comb. nov.ç Chaetoscypha nidulans Syd., Annales Mycologici 22, 305 (1924).= Pirottaea falcata P.R.Johnst., New Zealand Journal of Botany 36, 645 (1998).

As Chaetoscypha nidulans is the type (and only) species of Chaetoscypha Syd. 1924, this genus is now a synonym of Pirottaea Sacc. 1878.