Primary thallus: squamulose, persistent, forming large cushions; squamules: 3-6 mm long, 2-5 mm wide, entire to irregularly crenate-lobed to irregularly digitate lobed podetia: scarce to common, 14-55 mm tall, greenish gray, cup-bearing; cups: 2-9 mm wide, entire or with blunt to finger-like proliferations along margins, often simple and without proliferations but infrequently bearing one to three tiers of proliferations from center surface: smoothly corticate, squamulose or esquamulose, esorediate, slightly arachnoid in young parts Apothecia: uncommon, up to 3.5 mm diam, dark brown ascospores: narrowly fusiform, 10-16 x 2-3 micro meter Pycnidia: common, at cup margins, subglobose to ovoid, with hyaline gelatin conidia: 3-4 x 0.5-1 micro meter Spot tests: K- or K+ dingy yellow changing to brownish, C-, KC-, P+ brick red, UV- Secondary metabolites: fumarprotocetraric acid, occasionally with atranorin. Habitat and ecology: on soil or over duff World distribution: northern Africa, Asia, Europe and North America; mainly Mediterranean to temperate Sonoran distribution: eastern Arizona, Baja California, and southern California. Notes: Persistent primary squamules and usually poorly developed, short podetia distinguish this subspecies from subsp. verticillata, which is present further north in western North America (Hammer 1995). Specimens of C. cervicornis from California containing atranorin (in Santa Barbara and Amador Counties) were discussed in Hammer and Ahti (1990); their taxonomic status is still uncertain. Cladonia cervicornis probably includes more than two taxa in western North America, and is in need of further study. Here C. cervicornis is reported as new to Mexico.