Two oblique, colored arcs, convex toward the sun and tangent to the halo of 46° at points below the altitude of the sun. These arcs are produced by refraction (90° effective prism angle) in hexagonal columnar ice crystals the principal axes of which are horizontal but randomly directed in azimuth. If the sun's elevation exceeds about 68° the arcs cannot appear. A complementary pair of arcs, the supralateral tangent arcs, occasionally may be observed above the solar altitude.