proëtidæ

from The Century Dictionary.

• A family of medium-sized opisthoparian trilobites characterized by an oval, compact carapace, tumid caephalon, oval or ovate, tumid glabella with two basal lobes, thorax with 8–22 segments, and pygidium rounded and multisegmented. The family is represented by the genera Proëtus, Phillipsia, and Arethusina, which range from the Upper Silurian to the Permian system.