Calamus siphonospathus var. sublaevis Beccari.

Stems solitary, climbing, to 30 m, 2.5-5 cm in diam. Leaf sheaths yellowish brown, sparsely covered with needlelike, yellowish spines to 1 cm; ocreas membranous; knees obscure; flagella absent; rachis to 2 m with 25-50 linear pinnae per side, these regularly arranged and closely spaced; middle pinnae to 32 cm, to 2 cm wide at mid-point, adaxial veins and margins bristly; cirri to 1 m. Inflorescence to 0.6 m, not flagellate; inflorescence bracts open and swollen near apex. Fruits yellowish brown, ellipsoid, to 0.6 × 0.4 cm.

Scrub forests at low elevations. Taiwan (Lan Yu) [Indonesia, Philippines].