Psychotria inundata Benth. in Hook., Jour. Bot. 3: 229. 1841.
Psychotria setifera Benth. in Hook., Jour. Bot. 3: 228. 1841.
Psychotria arcuata Benth. in Hook., Jour. Bot. 3: 229. 1841.
It is not possible to separate P. capitata from P. inundata specifically, nor the various taxa (P. setifera, P. arcuata) proposed by Bentham from P. inundata. Intergradations occur between P. capitata subsp capitata and subsp inundata, but they differ mainly in the bracts of the inflorescence of P. capitata subsp capitata averaging longer and broader, the number of axes of the inflorescence of P. capitata subsp capitata fewer, and the inflorescence usually broader than high in P. capitata subsp capitata as contrasted with subsp inundata in which the inflorescence generally is longer than broad and averages longer throughout.
In the Flora of Peru (Field Mus. Publ. Bot. 13: 186. 1936) Standley treated P. inundata Benth. as a synonym of P. capitata R. & P., whereas in the Rubiaceae of Venezuela (Field Mus. Publ. Bot. 7: 450. 1931) he treats P. inundata as a valid taxon.