Complex sentence: This operculum structure has a corneous base with a heavy calcareous overlay, which in some genera has color or ornamentation of various kinds including, for example, pustules and incised grooves.
Split into simpler sentences: This operculum structure has a corneous base with a heavy calcareous overlay. The calcareous surface in some genera has color or ornamentation of various kinds including, for example, pustules and incised grooves.