Wikipedia
Pleuroctenium
Pleuroctenium is a genus of very small agnostid trilobites whose fossils are found in Middle Cambrian-aged marine strata of Canada (Newfoundland and New Brunswick), Czech Republic, England and Wales, France, and Sweden. Species of Pleuroctenium can be easily distinguished from all other agnostids because the frontal lobe of the central raised area of the headshield (or glabella) is wider than and folds around the rear lobe.