Craticula, formerly incorrectly named Graticula, is a genus of Palaeozoic coralline alga. They form the framework of reef rocks in the Silurian

Silurian

The Silurian is a geologic period and system that extends from the end of the Ordovician Period, about 443.7 ± 1.5 Mya , to the beginning of the Devonian Period, about 416.0 ± 2.8 Mya . As with other geologic periods, the rock beds that define the period's start and end are well identified, but the...

 of Gotland

Gotland

Gotland is a county, province, municipality and diocese of Sweden; it is Sweden's largest island and the largest island in the Baltic Sea. At 3,140 square kilometers in area, the region makes up less than one percent of Sweden's total land area...

, from the Högklint, Slite and Halla groups.

The Graticulaceae closely resemble the Cretaceous Solenoporaceae, and are only really differentiated by their stratigraphic position.

Graticula mineralized with calcite.