Campylopus jamesonii (Hook.) Jaeg., Ber. Tätigk. St. Gallischen Naturwiss. Ges. 1870–71: 422. 1872. Dicranum jamesonii Hook., Icon. Pl. 2: 179. 1837. Type. Ecuador, Surucucho, Jameson.
Campylopus standleyi var. lutescens Bartr., Contr. U.S. Natl. Herb. 26: 60. 1928. Type. Costa Rica, Prov. San José, Santa Maria de Dota, Standley & Valerio 43372 (FH, NY, US).
Plants robust, greenish yellow, growing in dense mats; stems moderately to densely tomentose, to 12 cm long, simple to sparingly branched. Leaves spreading below, erect-spreading above, concave when wet, flattened when dry, lanceolate-setaceous, to 20 mm long, serrate in upper ¼–½; costa excurrent, concolorous, to 4/5 the leaf width at base, smooth to lightly mammillose, in cross section guide cells well-developed, large ventral hyalocysts present, dorsal stereids well-developed; apical cells quadrate; median cells firm-walled, quadrate; basal cells near costa enlarged, firm-walled, not porose, elongate, those toward the margins smaller, firm-walled quadrate to rectangular, those at the margin narrower but not forming a distinct border, cells just above the alar cells enlarged, lax, square to short rectangular, frequently bulging; alar cells well-developed in large groups extending to the costa and frequently excavate. Sporophyte not seen.