The Lower Carboniferous has been traditlionally subdivided in Germany into three parts, cu I
 (Balvian), cu II (Erdbachian), and cu III (Aprathian).  The first correlates with the Lower Tournai-
 sian of the B elgian succession, the third roughly with the Upper Visean, starting with the entry of
 the genus Goniatites.  The Lower Carboniferous II, therefore, includes a long but poorly resolved
 time interval that is roughly an equivalent of the middle Courceyan to lower Asbian of the British
 subdivision or of the middle Kinderhookian to lower Meramecian of North America.  In the am-
 monoid succession this interval traditionally was thought to be represented by Pericyclus faunas,
 named after a family of unusually well ribbed early Goniatitina.  SCHMIDT (1925) subdivided the
 Pericyclus Stufe into four zones but these were never found in superposition but were based on
 widely separate assemblages from the "Kohlenkalk" of Belgium, the Waulsortian 'reefs' of Ireland,
 or the Erdbach Limestone of the Rhenish Massif (Germany).  In fact, the oldest true Pericyclus fall
  already in the Upper Tournaisian, leaving the Middle Tournaisian globally un-zoned, and the sup-
  posed youngest pericyclids later turned out to be derived nomismoceratids, leaving a Middle Viséan
  gap between the Pericyclus and Goniatites superzones.