In pure morphological terms, a dinocyst can be described as the body formed by the cyst wall, as well as the space it encloses and all the spaces within it. Cysts may develop their wall immediately within the theca, and such cysts are called proximate. Alternatively, the cyst may comprise a more or less spherical central body with processes or crests, and such cysts are termed chorate or proximochorate. Cysts may have a single-layered wall (autophragm), a two-layered wall (comprising an outer periphragm and an inner endophragm) or a three-layered wall (ectophragm, periphragm and endophragm if the outer wall is structurally supported, or otherwise periphragm, mesophragm and endophragm). Cysts with two or more wall layers that define a cavity are termed cavate. Excystment usually results in loss of part of, or an opening in, the cyst wall, termed archeopyle, the shape and position of which may indicate the position and/or shape of one or more thecal plates.