Back Side of Trimerus Trilobite

Here is the back thorax of a Trimerus type trilobite from the Silurian period. It is described in more detail on page 98 of the Fossils of Ohio book. According to that description, these trilobites could get to 20 cm in length. This one about 4-6 cm wide. The creature had small eyes about about 13 segments for the thorax.