Hydropunctaria rheitrophila (Zschacke) C. Keller et al.

    Thallus crustose, rather thin, sub-gelatinous when submerged, 0.06-0.1 mm thick, smooth, not cracked (except within herbarium), with minute dots or wrinkles possibly assembling in piles in some parts, grey-greenish, brown-greenish, olive-green, cortical pigment brown, white prothallus, seldom absent. Perithecia immersed, inconspicuous, hardly visible as minute black dots, 0.2  mm diam.. Spores simple, elliptical, 11-14 x 7-8 µm. Chemical spot test negative. On stones and rocks most often submerged in rivers and streams sections immediatly upstream estuaries. See Hydropunctaria scabra (Vezda) C. Keller & al. with a green pigment in the cortex and bigger ascospores, and also Verrucaria funckii which is greener and has much bigger ascospores and is more 'mountainous', developing in trout habitats.*