Diagnosis. Superficially similar to Lecanora galactiniza, but differs in having a distinctly developed pale brown hypothecium, a pale yellowish green thallus and in containing the xanthones thiophanic and 3-O-methylthiophanic acids.

Type: Ecuador. Galápagos: San Cristóbal, Pan de Azúcar, inland from Bahía Sardinas at the NW-coast of the island, 0˚43’13’’S, 89˚21’14’’W, 155 m alt., dry zone, E- to SE-exposed cliff at E-facing slope of the hill, on SE-exposed front of cliff of consolidated tuff, 24-Apr-2007, Bungartz, F. 6432 (CDS 34647–holotype).

Description. Thallus saxicolous, moderately thickened, verruculose areolate to bullate areolate; surface white to pale gray with a faint yellowish tinge, smooth, matt, epruinose, lacking soredia, prothallus absent. Apothecia numerous, often densely aggregated, circular in outline, 0.4–0.9(–1.2) mm in diam., adnate to sessile, often crowded, distinctly lecanorine, margin smooth to coarsely verrucose-crenulate, epruinose, concolorous with the thallus, disc plane to slightly convex, dark grey to black, epruinose; hymenium hyaline, not inspersed, epihymenium with a dark reddish to olivaceous brown pigment (ruginosa-brown: K+ deep reddish brown, HCl+ fuscous brown, N+ reddish brown), pigment ±persistent in K, lacking crystals (cf. glabrata-type); proper exciple thin, indistinct; thalline exciple thick, ±corticate, only with large crystals, insoluble in K (pulicaris-type); subhymenium hyaline, hypothecium pale to deep yellow; ascospores 8/ascus, simple, ellipsoid, (9.8)–10.7–13.2–(14.7) × (4.9–)5.3–6.6(–6.9) μm (n = 30). Pycnidia immersed, ostiole blackened (olivaceous black pigment), wall hyaline; conidia filiform, curved, 16.7–24.5 × ca. 1.0–1.5 μm (n = 6).

Chemistry. Thallus cortex P+ yellow, K+ yellow, KC+ yellow orange, C+ yellow orange, UV– (dull yellow); containing atranorin [minor], thiophanic acid [major], 3-O-methylthiophanic acid [major], zeorin [major]; [specimen analyzed with TLC: Bungartz, F. 6432 (CDS 34647–holotype)].

Etymology. Named in honor of Prof. Dr. Klaus Kalb, who first recognized that this species was superficially similar to, but not identical with Lecanora galactiniza.

Ecology and Distribution. Known only from the Galapagos; a single specimen collected on a sunny, exposed cliff in the dry zone of San Cristóbal.

Notes. Lecanora kalbii could be confused with L. galactiniza, but the thallus is pale yellowish because of the xanthones present. Unlike most Lecanora species, L. kalbii has a distinctly pigmented, pale brown hypothecium and this feature, together with the presence of xanthones might suggest that it belongs to Vainionora; its conidia are, however, clearly filiform.