Thallus: often bordered by a thin black prothalline line surface: chalky white to whitish gray, smooth, dull, continuous, often with fine cracks radiating from the perithecia and partly connecting them anatomy: undifferentiated, upper cortex indiscernible, algal cells 7-15 µm in diam., forming an irregular zone within the uppermost soft part of the rock Perithecia: completely sunken into pits in the rock and only the apex exposed which is slightly convex but hardly emergent, leaving empty pits after decay; exciple: subglobose or broadly pyriform, 0.25-0.40 mm wide, 15-20 µm thick, slightly thickened at the apex, black throughout, carbonaceous, ostiole inconspicuous; involucrellum: lacking; periphyses 20-30 µm long, ramified-anastomosing asci: clavate, 50-70 x 15-20 µm, 8-spored ascospores: hyaline, simple, ellipsoid, 18-25 x 9-13 Pycnidia: unknown Spot tests: all negative Secondary metabolites: none detected. Substrate and ecology: endolithic, in hard limestones and caliche from coastal to montane sites World distribution: central and southern Europe, Asia, northern and eastern Africa, New Zealand, and North America Sonoran distribution: scattered in Arizona (Coconino, Cochise, Graham, and Yavapai Counties), southern California (Riverside Co.), and Baja California. Notes: The type specimen has a small lid-like involucrellum and represents Bagliettoa parmigera (Renobales 1996). The correct name for Verrucaria calciseda auct. remains uncertain as the species belongs to a poorly-known group. Verrucaria hochstetteri is similar, but has larger perithecia and spores, and the bases of exciples often remain in the empty pits after the perithecia have fallen out. The lichenicolous fungus Polycoccum opulentum is often found growing on Verrucaria calciseda.