smooth, thick, finely chinky or tiny areolate, covered with tiny black projections or “pegs,” rarely smooth, dull or slightly shining, occasionally brownish black. Perithecia
small, 0.3-0.7 mm, in slightly raised parts of the thallus, with punctate ostiole; exciple
spherical, black; a black involucrellum forming a raised hump in the thallus and spreading laterally in the thallus, over half or more of the perithecium; gelatin 1+ red; spores ellipsoid or elongate-ellipsoid, 10-20 x 7-10 µm.
This species is found on acid rocks along sea shores, in the surf-swept zone. It is circumpolar arctic to temperate. Fink (1935) reported it as south to New England in the East and to California in the West.
This is an extremely variable species (see Taylor 1982). A variant with very thin thallus and prominent perithecium, named Verrucaria prominula Nyl. in Mudd (Man. Brit. Lich. 291. 1861), was listed by Nylander (1887 (1888)) as occurring at Port Clarence, Alaska, but should be included here (Taylor 1982).