Article: Upper Ordovician trilobites from northern Yukon

The trilobites Robergia yukonensis sp. nov., Cryptolithoides, and Ampyxina salmoni Churkin are described from the Road River Formation. They occur above the Ashgillian (Late Upper Ordovician) graptolite zone of Dicellograptus complanatus var. ornatus and below beds containing the graptolite Climacograptus scalaris var. normalis of possible earliest Silurian age. Robergia and Cryptolithoides, although widely distributed geographically, have hitherto been reported from only Middle or presumed Middle Ordovician beds, and as a result have been considered reliable indices of that series.