Genus Pyrgillus Nyl.

Thallus crustose, ecorticate, algae Trentepohlia, apothecia with dark more or less cylindrical raised excipulum, asci cylindrical, 8-spored, spores brown, ellipsoid or fusiform, 1- or 3-septate, forming well-developed mazedium.

Pyrgillus crassus Murray, sp. nov.

Thallus lignicolus, crustosus, crassus, rimosus, albidus vel cinerescenti-albidus, ecorticatus, major minusve homoeomerus, hypothallo nullo, K-, P-, gonidiis Trentepohlioidis irregulariter subglobosis ad 13 × 9μ, in coloniis. Apothecia elevata, subcylindrica, nigra, epruinosa (vel apothecia juventia subglobosa, albido-pruinosa ad ostiolem), excipulo obscure fusco, subtendente hypothecium et K + brunneus; sporae fuscae, biloculares, oblongae, ad septo constrictae, 11½–18½ × 8–8½μ Pycnidia non visa.

Thallus crustose, subeffigurate, to 10 cm dia., white to greyish-white, without distinct hypothallus, rimose (in dry state) forming irregular areolae 200–800μ across, 300–400μ thick; apparently ecorticate but with outer hyaline decomposed layer 5–15μ thick, algae green or yellowish-green, Trentepohlia, subglobose 10–13μ dia. to oblong 13 × 9μ with thin sheath and forming clumps embedded in the nubilated “decomposed” tissues of upper part of the thallus; medulla mostly of disorganised structure but some 2½μ dia. hyphae visible in KOH; K.-P.- Mature apothecia black, 500–700μ dia., raised about 300μ above thallus, slightly conic, excipulum matt or faintly shining, 35–40μ thick at sides increasing to over 100μ beneath hypothecium, very dark brown in section with outer part lighter and a surface hyaline coating 5μ thick, K + brownish., hypothecium indistinct, 60μ thick including bases of old asci; asci cylindrical, 8-spored, evanescent; spores smoky brown, 1-septate, distinctly constricted at septum, oblong, 11½–15½ × 8–8½μ with wall and septum 1–½2μ thick, contents grumose (spores clearing and turning dark brown, swelling to 18 × 10½μ in KOH)., mazedium at least 250μ thick, black, K + faint brown.

Habitat. On dead wood.

Distribution. Otago: Green Hill (Silver Peaks), 2,000ft, 4203.

Although this new species has been collected only once, it is moderately common on a line of old fence posts in the type locality. There are only two other species in the genus with 2-celled spores, both from near Brisbane, Australia; the Northern.