Phacops Trilobite (close-up of the head and eye).
This Trilobite has an Holochroal Eye design, found in all orders of trilobites. Trilobites were similar to the modern day Wood Louse only sea dwellers. They came in many different sizes ranging from 1″ inch to around 1 metre in length.
Size of the Trilobite 2 1/2″ x 1 1/2″ inches.
Trilobites had compound eyes (made up of many lensed units) made from Calcite crystal, developed through many millions of years. Early species a sub order Agnostida from the early Cambrian Period 520 million years ago were eye-less.
The group Phacopida ranged from the late Cambrian Period 500 million years ago to the late Devonian Period 380 million years.