A new lichen species is described from specimens growing on Fraxinus trees north of Eindhoven (the Netherlands). Morphological and genetic studies suggest that the new species belongs in the genus Catillaria, and the name Catillaria flexuosa is proposed because of its flexuose apothecia. The new species is characterized by the relatively large apothecia (up to 0.9 mm diam.) and relatively thick, knobby to ±subsquamulose, greenish, thallus. Due to their similar morphological features, C. flexuosa can be easily confused with Catillaria chalybeia, C. fungoides or C. nigroclavata, so it is therefore compared with these species. In addition, Arthonia epiphyscia is reported being a very rare species in the Netherlands.
