M. subtriloba Gleason, Bull. Torrey Club 58: 429. 1931.
This widespread species is now known in the Guayana area from several Schultes collections in the Vaupes drainage, from the slopes of Cerro Duida, and from the Neblina slopes (Maguire, Wurdack & Maguire 42017). Two isotypes (Martius Herb. Fl. 498) have been examined and show predominantly 4-merous flowers, as do other specimens over the species range; the original description of 5-merous flowers was probably based on one of the few anomalous flowers always found in a large collection series.