A crustose species with a green to dark olive-green thallus that is smooth and appears oily. The white prothallus may also be visible between the cracks in the thallus. The black perithecia are immersed but may become more prominent when dry.
Verrucaria mucosa is widespread along the Scottish coast where it grows among barnacles on well-lit maritime rocks in the littoral zone. BLS distribution map
scottishlichens.co.uk 