Gerastos is a genus of proetid trilobite in the family Proetidae that lived between the Pragian and Eifelian of the Lower-Middle Devonian, spanning approximately 21 million years.
Gerastos has holochroal eyes situated to the side of its enlarged glabella region of the cephalon. The surface of the cephalon can be smooth or covered with pustules. Length rarely exceeds 3 cm. == References ==