Polymeridium submuriforme is a species of corticolous (bark-dwelling) lichen in the family Trypetheliaceae.

This ecorticate lichen is characterized by its pinkish-grey thallus, which does not fluoresce under ultraviolet light.

P. submuriforme is similar to Polymeridium cinereonigricans but can be distinguished by its much smaller ascospores and inspersed hamathecium.

The ascomata measure 0.3–0.6 mm in diameter, with a solitary, spherical centrum that is erumpent.

These ascospores are not ornamented and are surrounded by a 1–2 μm wide gelatinous sheath.