Verrucariaceae Bagliettoa baldensis (Verrucaria baldensis) Growth type crustose. Chemical results negative. Common on hard limestone rocks and memorials, shells and mortar. Uncracked white or pale grey thallus with abundant small, almost immersed, perithecia (0.3mm diam) that leave small pits when they decay. Ostioles have 3 to 6 radiating cracks (visible with 20x lens). The thallus is surrounded by a narrow, dark prothallus. Asci 8-spored, spores simple. Sometimes host to Opegrapha rupestris and Toninia verrucariae Similar: Verrucaria hochstetteri, larger perithecia, to 0.8mm diam. Bagliettoa calciseda (Verrucaria calciseda)

Bagliettoa baldensis (Verrucaria baldensis)
Parkstone, Dorset. March 2012 and on cockle shell, Hampshire, November 2013