A rare early fenestellid bryozoan colony, from Middle Ordovician rocks near Llandrindod. In a relatively deep, muddy environment, this was living attached to the empty shell of a nautiloid. It's about 2 cm wide.
One of the most common genera of trilobite in the Ordovician Builth Inlier. The white crystals are gypsum, growing over the fossil during weathering.