Acaste_(genus)
Acaste is a genus of extinct trilobite of the order Phacopida which lived throughout the Silurian period (Wenlock Group).[1] Though many species had been included, it now has only one species, Acaste downingiae.[2] It is characterized by a convex dorsal surface, an absence of spines, a shortening of the head-shield and a general rounding off of all angles.[3]