THE LICHID TRILOBITE RADIOLICHAS IN THE SILURIAN OF ARCTIC CANADA ANDGOTLAND, SWEDEN

Radiolichas has been a poorly known and exclusively Devonian genus of very limited diversity. Radiolichas raydaviesi sp. nov. and R. davedav iesi sp. nov. are the best-known members of the genus, and extend its stratigraphic and geographic range to the Wenlock of the central Canad ian Arctic. A further Silurian occurrence is an unnamed species from t he Wenlock Slite Beds of Gotland, Sweden. Radiolichas is most similar to Dicranogmus. Together, the genera lack any of the robust trochurine apomorphies (linear pygidial postaxial ridge, prominent pygidial bord er, prominent cranidial fossula) and appear to fall outside the phylog enetic structure of that subfamily. They are similar to members of the Tetralichinae, particularly in pygidial features, but lack the compos ite cranidial lobe characteristic of that subfamily. Their systematic position is presently unresolved.