Circulus is a psychedelic folk/progressive rock band from South London, England, put together by vocalist and songwriter Michael Tyack. Circulus believe that the high life is actually mediæval life. This is reflected in their varied work, which they describe as "hurtful to people's ears."

A concentric ridge formed on a scale by the periodic addition of material to the edge of the basal plate. The circuli on scales may be continuous or segmented by the scale radii, in which case the individual segments are termed platelets. Circuli are formed only on the outer surface of the scale; the inner surface is smooth. Circuli formed on bivalves are concentric, scalloped ridges which become crowded together at an annulus.