Verrucaria macrostoma f. furfuracea forme sur béton.

    This form is found on concrete works subjected to seaspray on the foreshore (peers, dikes, embankments, etc.) where it forms large and well developed  colonies with rather thick squamulose areoles, brown-ochre when dry and most often brown-olive to greenish when moist or sprayed by seawater. Marginal blastidia, usually isidioid, are brown-gold, and sometimes may entirely cover areoles.