For »Cystidean Limestone» (Törnquist 1871, Syn. »Echinosphaerites Limestone» of Tullberg 1882, »Older Chasmops Limestone» of Wiman 1907, »Lower Chasmops Limestone» of Thorslund 1938; middle part of Middle Ordovician) the new name Ludibundus Limestone (after Asaphus ludibundus Törnq.) is proposed.