A dusting of powdery material and the presence of occasional scales on the central axis of its leaves help distinguish it from related species.

[1] It bears linear-subulate (awl-shaped)[2] or lanceolate scales,[1] 3 to 5 millimeters (0.1 to 0.2 in) long and acuminate at the tip, with entire (toothless) margins.

[1][2] The rachis (leaf axis) has sparse white farina (powder) scattered on its surface and occasional narrow scales about 1 millimeter (0.04 in) long.

[1][2] Each blade has 7 to 12 pairs of pinnae, which are widely spaced, lanceolate[2] to narrowly oblong in shape, with a short stalk at the base, or none at all, connecting them to the rachis.

[3] It was first described by William Ralph Maxon and Charles Alfred Weatherby in 1939 as Notholaena peninsularis, based on material collected in Baja California.

[5] Both Edwin Copeland and Weatherby suggested in the 1940s that this group of ferns might represent a distinct genus of its own.

[8] In 2018, Maarten J. M. Christenhusz transferred the species to Hemionitis as H. cairon (the epithet peninsularis was preoccupied), as part of a program to consolidate the cheilanthoid ferns into that genus.