[TA] a thin sheet of white matter, hidden by the cerebellar tonsil, attached along the peduncle of the flocculus and, at or near the midline, to the nodulus of the vermis; it is continuous caudally with the epithelial lamina and choroid plexus of the fourth ventricle. SYN: velum medullare inferius [TA], posterior medullary velum, Tarin valve, valvula semilunaris tarini, velum semilunare, velum tarini.