A cephalopod limestone intercalation in the Early Famennian Lagów beds of
Janczyce (eastern Holy Cross Mountains, Poland) contains, in each of its five
layers, abundant fossil assemblages of goniatites.  The lineage of Tomoceras is
especially well represented there. lt starts from typical T. frechi with rounded
venter and ends in T. subtentifome with sharp-edged venter.  A bed-by-bed
biometrical study has shown a bimodal size frequency distribution of conchs in
each layer which is interpreted as sexual dimorphism.  T. frechi parvum
subsp. n. and T. subacutum sp. n., are proposed new forms that represent
successive connecting links within the lineage.