The cephalopods of the Boda Limestone, Late Ordovician, of Dalarna, Sweden Author Kröger, Björn text European Journal of Taxonomy 2013 2013-03-27 41 1 110 journal article http://dx.doi.org/10.5852/ejt.2013.41 386010a0-6da4-4fa3-9d1a-4b3b5427cac5 2118-9773 3814221 A2F1B9ED-870A-466E-B35E-BD5DA782476E Genus Tyrioceras Strand, 1934 Type species Tyrioceras kjaerulfi Strand, 1934 , Furuholmen, Asker District, Norway , Grimsøy Formation, late Katian, Late Ordovician; by original designation. Emended diagnosis Large straight, compressed to depressed conch cross section; ornamented with broad bands or narrower raised transverse lines, which form broad and well marked, but not very deep ventral sinus with ventrolateral and dorso-lateral salients, siphuncle eccentric; septal necks orthochoanitic, relatively long, siphuncular segments tubular. Remarks The external characters of this genus where described in detail by Strand (1934) and Frye (1982) . Originally the diagnosis of the genus was based only on the type species. In order to include T . warburgae Frye, 1982 , which is similar to the type in many aspects, but differs in having a depressed, more rapidly expanding conch, the diagnosis is emended. The placement of Tyrioceras within the Lituitina , was formerly based on the characteristically curved ornamentation alone, and therefore was somewhat questionable. The details of the internal characters, now known from T . warburgae , support these earlier assumptions. The shape and extent of the cameral deposits in T . warburgae are very similar to those of other lituitins. A syn-vivo dissolution of the connecting ring, which is typical of lituitins, is indicated by epichoanitic deposits ( Figs 29 , 30 ). Additionally, voluminous epi-, hyposeptal and mural deposits, and relatively long septal necks are very characteristic for Lituitina . The assignment within the family of Sinoceratidae is after Dzik (1984) .