1b. Didymodon rigidulus var. subulatus (Thériot & E. B. Bartram) R. H. Zander, Cryptog. Bryol. Lichénol. 2: 395. 1981.
Didymodon mexicanus var. subulatus Thériot & E. B. Bartram, Bryologist 29: 1, plate 1. 1926
Stem leaves appressed to weakly spreading when dry, long-lanceolate, evenly broadened, long-oval; costa excurrent as a subula; proximal cells rectangular; distal laminal cells smooth, with quadrate lumens, lamina 2-stratose in distal 1/2-3/4; gemmae absent. Peristome teeth short, rudimentary, of 16 oval teeth with 1-2(-4) articulations.
Capsule maturity unknown. Rocks, ledges, soil, canyons; moderate to high elevations (1000-2000 m); Ariz., Tex.; Mexico (Distrito Federal, Michoacán, Puebla, Querétaro, Sonora).
Variety subulatus is similar to var. icmadophilus in leaf shape and most other characters, and intergrades occur. It may be regarded as a somewhat distinctive geographical variant. The variety phenocopies Grimmia hamulosa, which differs by the grimmiaceous peristome, homogeneous costal section, and more robust habit.