 The dorsal surface of the trilobite cephalon (the frontmost tagma, or the 'head') can be divided into two regions—the cranidium and the librigena ("free cheeks").The cranidium can be further divided into the glabella (the central lobe in the cephalon) and the fixigena ("fixed cheeks").The facial sutures lie along the anterior edge, at the division between the cranidium and the librigena.