Basionym: Pleurothallis affinis Lindley (1836: 354).

TYPE:— PERU. Dept. of San Martín: lithophytic, Province of Chachapoyas, 1835, Mathews 1899 (holotype: K!).

Homotypic synonym: Humboltia affinis (Lindl.) Kuntze (1891: 667), as “ Humboldtia ”.

Heterotypic synonyms: Pleurothallis rigidifolia Reichenbach (1855b: 224). Humboltia rigidifolia (Rchb.f.) Kuntze (1891: 668), as “ Humboldtia ”.

TYPE:— PERU. San Martín: lithophytic near Chachapoyas, 1840, Mathews 3187 (holotype: G!).

Pleurothallis furfuracea Lehmann & Kraenzlin (1899: 441).

TYPE:— ECUADOR. Morona Santiago: Andes east of Sigsig, 1887, Lehmann 6511 (holotype: K!; isotype: AMES!).

Distribution:— Costa Rica, Colombia, Ecuador, Peru and Bolivia.

Notes:— The illustration of M. affinis in Luer (1992) based on a plant collected in Ecuador is similar to that presented here in Fig. 12A, also from Ecuador. However, the type of M. affinis was collected in Peru. As indicated by Luer and demonstrated by several of his sketches at SEL, this species is highly variable. The material of M. affinis recently described and illustrated from Costa Rica (Rojas-Alvarado & Karremans 2017) is clearly similar to some of Luer’s drawing of this species, but also similar to some of Luer’s drawings of M. dasyllis (all at SEL). Some differences between the diverse material are evident, with specimens from Costa Rica being morphologically more consistent with the type specimen of P. furfuracea than with that M. affinis. It is possible that more than one species is currently treated under the name M. affinis, but with the available information it is impossible to separate these entities. Specimens from the type locality of M. affinis in Peru and M. dasyllis in Ecuador need to be examined carefully, and a thorough study of the variation of this species across its distribution is needed.