Two different probably depth- and/or facies-related morphological groups are recognized within the "shallow water" genus Icriodus of the Belgian Famennian: the " Icriodus alternatus group" dominates in the relatively quiet offshore marine sediments of the Lower Famennian ("Groupe des Schistes de la Famenne "), where as the " Icriodus cornutus-costatus group" characterizes the more nearshore, turbulent facies of the Upper-Famennian ("Groupe des Psammites du Condroz"). A probable endemic morphological evolution is suggested for the latter group. A phylomorphogenetical lineage has been observed between I. alternatus BRANSON & MEHL and I. cornutus SANNEMANN at the base of the Famennian. The interspecific morphological relations and the intraspecific morphological variability within the different Icriodus -stock are discussed. Three new morphotypes of I. alternatus , one new subspecies of I. cornutus and two new subsepcies of I. costatus (THOMAS) are described; their stratigraphical range is discussed.