The perineural sheath (neural lamella or perineurium in invertebrates) surrounds and protects the central nervous system, particularly in invertebrates. In vertebrates, the CNS is protected by the meninges (dura mater, arachnoid mater, pia mater). The perineurium surrounds individual nerve fascicles in peripheral nerves; the peritoneum lines the abdominal cavity; perichondrium covers cartilage.