Thallus: foliose to caespitose-subfruticose, rarely exceeding 3 cm in diam., very loosely adnate, irregularly lobate lobes: mostly paddle-shaped, up to 3 mm broad, broadest near the tips, simple or weakly branched, often ascending apically, sometimes elongate and linear but tips sometimes helmet-like, ciliate; cilia: marginal and laminal, up to 6 mm long upper surface: whitish gray, uneven, ± pruinose, sometimes minutely bullate, sorediate soredia: farinose, in soralia on the underside of the whole lobes or sometimes on recurved lobe-tips or breaking through the upper cortex upper cortex: prosoplectenchymatous medulla: white, lower part often agglutinate and appearing like a cortex lower cortex: absent lower surface: white, sorediate, often vein-like due to downward extension of the upper cortex, erhizinate (although cilia may be misleading) Apothecia: occasional, up to 3 mm diam., short stipitate, margin mostly ciliate; disc: black, plane, often pruinose asci: subclavate to clavate, 8-spored ascospores: brown, l-septate, ellipsoid, Physcia-type (15-) 15.5-18 (-19.5) x (6.5-) 7- 8.5 (-9.5) µm Pycnidia: ± common conidia: usually bacilliform (but sometimes pointed at one end), 4-5 x <1µm Spot tests: cortex K+ yellow C-, KC-, P+ yellow; medulla K+ yellow, C-, KC-, P- Secondary metabolites: cortex with atranorin and chloroatranorin; medulla with atranorin and zeorin (minor to ± accessory). Substrate and ecology: on shrubs, seems to prefer coastal sites in the Sonoran Desert area World distribution: SW North America and South Africa Sonoran distribution: Channel Islands of California and coastal areas of Baja California, Baja California Sur and southern Sonora. Notes: The species is recognized by the ± helmet-shaped lobes with soredia on the underside, its ciliate lobes and its small size. The presence of soredia readily separates it from H. erinacea. See Essinger and Bratt (1998) for a discussion of other, subtle morphological differences.