 As such, they became secondarily blind in this branch of trilobite evolution.Other trilobites (e.g., "Phacops rana" and "Erbenochile erbeni") had large eyes that were for use in well lit, predator-filled waters.The pair of antennae suspected in most trilobites (and preserved in a few examples) were highly flexible to allow them to be retracted when the trilobite was enrolled.