Myriospora westbergii (Acarosporaceae), a new discovery from the Galapagos Islands, Ecuador.
Myriospora westbergii is described from the Galapagos Islands where it is considered to be endemic. It differs from other species of Myriospora by its emergent apothecia with a distinctly elevated thalline margin that increasingly blackens from the inside. The species is most similar in general appearance to M. hassei, a lichenicolous lichen parasitic on Acarospora socialis which occurs along the coast of California. The new species is clearly distinguished from M. hassei by its unusual apothecial anatomy and ontogeny and in having orange pruina occasionally covering the apothecial disc and margin. The epicortex in Acarosporaceae is discussed. Myriospora westbergii is the 28th species of Acarosporaceae we have reported from South America.