Trilobites

Trilobites are extinct arthropods which first appear in the lower Cambrian. They reached their peak in the Silurian and after a slow decline, disapeared in the Permian.

These creatures moulted their exoskeletons at regular intervals. Most fossil finds are either the Cephalon or Pygidium, the Thorax having disintegrated into separate segments.

This is a fairly common fossil from the Silurian rocks near Ludlow in Shropshire, England. Dalmanites was a small trilobite that probably forraged on the sea bottom. Because of the need to watch for larger preditors it developed very keen eyesight.

This is a magnified view of the compound eye of Dalmanites. Even after 400 million years, some details of the complex structure is still visible. Because of the semicircular curvature and conical shape of this trilobites eyes it would have had a complete view of its surroundings. The streamline shape of its body implies that it could burrow into the sand on the approach of a predator.

Calymene.

This is an enrolled specimen from Morrocco. No I never got it there, I bought it in Mr Wood's Fossil Shop in Edinburgh.