R. linearis K. Schumann in Martius, Fl. Bras. 4: 296 (1890)

Info from Backeberg's Lexicon
Reduced to synonymy under L. warmingianum by Barthlott and Taylor Bradleya 13

• Body. shrubby, 60 - 80 cm long., branching from the sides;
• Shoots very narrow, linear, 5 - 20 cm long., 4 - 7 mm broad, with a stout mid-rib, distinctly notched;
• Areoles. weakly felty, without bristly spines;
• Flowers . lateral, funnelform or rotate, to 1.8cm long, white to yellowish;
• Ovary. ellipsoid, naked;
• Fruit. spherical, translucent, white, 5 mm diam.
• Habitat - Brazil (in the south, no locality stated); Paraguay (on the Rio Yhu and near Caaguazu); Argentina (Misiones).