Geisonoceras sp. from the Silurian of Poland. 1. Living chamber in ventral view, Late Silurian, borehole Białopole IG (depth of 1670.7 m). 2. Phragrnocone in lateral view (a) and its medial section (b), upper Siedlce beds, Ludlow, borehole Gołdap. 3. Longitudinal section through the siphuncle; erratic boulder, probably early Ludlow, Orłowo.

Geisonoceras sp. from erratic boulder E-116, of Baltic origin from Rozewie, Poland, P. originalis Zone, Volkhovian; reconstruction of the adult body chamber (a); reconstruction of a phragmocone fragment with calcareous deposits (b) and section through the siphuncle of the same specimen (c) from boulder E-116, Rozewie.