Geisonoceras Hyatt, 1884

Kröger, Björn, 2013, The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden, European Journal of Taxonomy 41, pp. 1-110 : 43-44

Genus Geisonoceras Hyatt, 1884

Type species

Orthoceras rivale Barrande, 1866 , Prague Basin, Czech Republic, Ludlovian, Silurian; by original designation.

Diagnosis

Slender longiconic orthocones or slightly cyrtoconic longicones with circular to subcircular cross section; ornamented with broad transverse bands between which are fine growth lines; transverse bands are slightly oblique forming shallow hyponomic sinus; sutures directly transverse or slightly

oblique; siphuncle subcentral; septal necks short orthochoanitic; connecting rings slightly expanding within chambers; weak annulosiphonate deposits concentrated at septal foramen in adapical siphuncular segments; camerae with episeptal and hyposeptal deposits. (Adopted from Sweet 1964c).