The premotor cortex is dysgranular: it contains a faint layer IV. The premotor cortex can be distinguished from Brodmann area 46 of the prefrontal cortex, just anterior to it, by the presence of a fully formed granular layer IV in area 46.The premotor cortex is therefore anatomically a transition between the agranular motor cortex and the granular, six-layered prefrontal cortex.he premotor cortex occupies the part of Brodmann area 6 that lies on the lateral surface of the cerebral hemisphere. The medial extension of area 6, onto the midline surface of the hemisphere, is the site of the supplementary motor area, or SMA.
A Nilos ring is an external metal bearing seal that produces a small labyrinth like sealing surface on the inner or outer ring of a bearing. When mounted in pairs, the bearing is sealed for life.
There are three main rings which are very thin and dark. The rings are made up of small rocks and dust. Neptune's rings are not the same thickness all around. There are areas of the rings which are much thicker than other areas of the rings. These thicker parts are called ring arcs. Some of these ring arcs are also twisted. Because Neputune's rings are so dark and faint, they were not discovered until the 1980s.