East of the crossing are four rectangular bays terminating in a semicircular apse. The dorsal component forms the utricle and semicircular canals. The doorways are placed within semicircular arches. Angular accelerations are detected by semicircular canals. During this transition, the abdomen changes from a triangular to a semicircular shape. There are two types; semicircular and triangular. These connect to the semicircular canals and the cochlea. Guards were either semicircular or straight, but always highly ornamented with geometrical patterns. These windows have large lights contained in tracery of a semicircular form, like overlapping petals. The endolymph surrounds the ampullary cupula which contains hair cells within the semicircular canals. Somatogyral illusions occur as a result of angular accelerations stimulating the semicircular canals. The cupula is located within the ampullae of each of the three semicircular canals. The semicircular canal system detects rotational movements. The principal entrance was under a semicircular archway. Each facet has a window in the form of a semicircular arch.