Gyrostomum scyphuliferum

The genus Gyrostomum contains only this one species. It is known from Florida, South Carolina, Louisiana, Alabama and Texas. The thick black part on the sides and under this thin section is the exciple. The hymenium is the upper clear part. Its longitudinal lines are called "paraphyses". The hypothecium is the thin area with the roundish yellow-green cells.  Most dichotomous keys used to identify the Graphis lichens divide them by whether or not they contain round oil droplets in the hymenium.  Gyrostomum lacks these droplets.