Geonoma riojensis Henderson, sp. nov. TYPE. PERU. San Martín: Rioja Province, Pedro Ruiz-Moyobamba road, km 390, Venceremos, 5°50´S, 77°45´W, 2040 m, 2-3 Aug 1983, D. Smith & S. Vasquez 4590 (holotype: MO!).

Plant height 2.5, n = 1; stems no data; stem diameter no data; number of leaves per stem no data. Leaves green, without a dense covering of gray tomentum, regularly pinnate with narrow, 1-veined pinnae; petiole length no data; rachis length 38.0 cm, n = 1; rachis width 2.7 mm, n = 1; number of leaf divisions per side of rachis 14, n = 1; basal angle of pinna divergence 73°, n = 1; basal pinna length no data; basal pinna width 0.3 cm, n = 1; basal pinna thickness no data. Inflorescences branched; prophylls and peduncular bracts swollen, short, not sheathing the peduncle, early dediduous; prophyll margins without curved fibers; prophyll length 9.7 cm, n = 1; peduncular bract length 10.3 cm, n = 13; distance between bract scars 1.3(0.8-1.7) cm, CV 0.5, n = 2; peduncle length 16.1(12.6-19.5) cm, CV 0.3, n = 2; peduncle width 2.9(2.8-3.0) mm, CV 0.1, n = 2; orders of inflorescence branching 2, n = 2; rachilla width 2.8(2.6-2.9) mm, CV 0.1, n = 2; number of rachillae 17(11-24), CV 0.5, n = 2; flower pits not raised, the rachillae not narrowed between the pits; upper lips of pit present; fruits no data.

Distribution. From 5°45´-5°50´S and 77°40´-77°45´W at a mean elevation of 1945 (1850-2040) m on western Andean slopes in northern Peru (map).