The new Tremella imshaugiae, lichenicolous on Imshaugia aleurites, is described from Scotland and Maine (USA); it is characterized by small, 0.1–1 mm diam., amber coloured basidiomata not inducing gall-formation, 2–4-celled, mainly longitudinally septate basidia, 15.5–21.5 × 13–16.5 μm, and relatively large, subspherical basidiospores, 6.5–9 × 6.5–8.5 μm; it is sister to T. diploschistina in a phylogeny using ITS and nLSU markers. The new Tremella tubulosae, lichenicolous on Hypogymnia tubulosa, is described from Scotland and Spain; it is characterized by pale to dark brown or blackish basidiomatal galls, 0.2–1.8 mm diam., 2-celled, mainly longitudinally septate basidia, 10–17 × 8–11 μm, and mediumsized, subspherical to ellipsoid basidiospores, 6.5–8 × 5–6.5 μm; it is sister to T. hypogymniae in a phylogeny using ITS and nLSU markers.