Plants 10–50 cm tall. Leaves 2–6, basal, petiolate; petiole l–4(7) cm long; blade up to nine cm long and 3.3 cm wide, commonly smaller, elliptic to lanceolate-elliptic, more or less oblique, acute to obtuse, glabrous. Peduncle erect, glandulose-puberulent above basal third, completely covered with approximate sheaths, terminated by a subdensely many-flowered, cylindrical raceme. Flowers greenish to greenish-white, sepals glandulose-pubescent externally. Floral bracts up to l4 mm long, ascending, ovate-lanceolate, acute to acuminate, glandulose-puberulent. Pedicellate ovary up to 22 mm long, glandulose-puberulent, ascending. Dorsal sepal up to seven mm long and 2.5 mm wide, lanceolate-elliptic to ovate-lanceolate, acute to subobtuse, 3-veined. Petals subsessile, blade up to seven mm long and four mm wide, obliquely triangular-ovate, more or less attenuate towards apex, rounded at distal end, basally truncate, apically connivent with dorsal sepal, margins distinctly but minutely ciliolate, 3-veined, veins branching. Lateral sepals up to eight mm long and three mm wide, free to the base, obliquely ovate to oblong ovate with more or less falcate apex, acute to subacuminate, 4-veined. Lip shortly unguiculate to subsessile; lamina up to five mm long and up to four mm wide when expanded, cymbiform, deeply concave, transversely elliptic in general outline, subcordatem at base, truncate at apex, apically provided abruptly with a fleshy, conduplicate, elongate, deltoid or spathulate, acute apical lobule, disc densely papillose, margins thin, glabrous. Gynostemium up to five mm long in total, basaly shortly stalked (Figs. 4 and 5).

Ecology: Terrestrial. Flowering in February, May, and December.

Notes: P. rostrata can be distinguished from other species of this group by having subsessile lip with transversely elliptic lamina, devoid of any calli, except papillose protuberances on disc. The petals are relatively large, subsessile with minutely ciliolate margins, more or less triangular in general outline, attenuate towards apex, with rounded distal end and truncate base. It can be easily confused with P. micromystax and P. camargoi described below. Both species, however, have unguiculate lip and auriculate petals.