The veliger larva has a shell and ciliated velum. They are bridged by the superior medullary velum. Velar consonants are made using the tongue body against the velum. The velum is raised so that air cannot flow through the nasal cavity. A postnasalized stop begins with a raised velum that lowers during the occlusion. The velum sometimes leaves a partial annular (ringed) zone. "Cumulus velum" clouds have an ice crystal veil over the growing top of the cloud. A prenasalized stop starts out with a lowered velum that raises during the occlusion. Velopharyngeal insufficiency includes any structural defect of the velum or mechanical interference with closure. Materials used were often leather, velum, or paper. It has a ridge-like structure on the inner margin, called a velum. If the velum is present, it is called a craspedote medusa.