Final answer:
The periosteal and meningeal layers of the dura mater do not fuse at the foramen lacerum, which is an aperture in the skull filled with cartilage.
Step-by-step explanation:
The periosteal and meningeal layers of the dura mater are indeed fused at several points within the cranial cavity to form structures that compartmentalize the brain. The falx cerebri and the tentorium cerebelli are two such infoldings where these layers are fused. However, they are not fused at the foramen lacerum, which is an aperture in the base of the skull that is filled with cartilage and does not transmit any major vessels or nerves. In contrast, the foramen magnum, the large opening at the base of the skull, is surrounded by the layers of the dura mater, reflecting another point of fusion.