Cycloceras

Cycloceras is an extinct nautiloid cephalopod genus from the Carboniferous of Western Europe, (Ireland and Scotland) of unknown affinity with the orthocerida (Sweet 1964 in) 
Taxonomy.
"Cycloceras" was named by McCoy (1844 and assigned to the Michelinoceratida by Flower (1962)and to the Orthocerida by Sweet in Teichert et al. (1964);
"Cycloceras" is possibly a member of the Cycloceratidae and may be synonymous with "Perigrammoceras" Foerste
Morphology.
The type species of "Cycloceras", "C. annularis", is based in an internal mold of a body chamber on which the position of the siphuncle is indiscernible (Sweet 1964,) Species referred to Cycloceras are annulated, subcylindrical orthocones with no longitudinal ornamentation . Fig 186, p K258 Teichert et al. (1964) shows "Cycloceras" as narrow, gently expanding, annulated othocone with a narrow subcentral siphuncle. Annuli (circular transverse bands or costae) are thick and close spaced, giving a corrugated appearance.