Article: The trilobite Lejopyge Hawle and Corda and the middle–upper Cambrian boundary
The species and subspecies of the late middle Cambrian agnostid trilobite Lejopyge are reviewed. Lejopyge cos Opik is shown to be a junior synonym of Lejopyge laevigata armata. In Sweden the middle-upper Cambrian boundary is placed at the boundary between the Lejopyge laevigata and Agnostuspisiformis Zones. The reassignment of L. cos to L. l. armata and other criteria suggest that this boundary in Australia should be drawn within the Mindyallan Cyclagnostus quasivespa Zone between the L. cos and Blackwelderia sabulosa faunas.It is suggested that the middle-upper Cambrian boundary in North America be placed well up into the Cedaria Zone; in China it is at some as yet undefined position within the Blackwelderia sinensis Zone; on the Siberian Platform it should be placed between the zones of Lejopyge laevigata armata-Lomsucaspis alta and Agnostus pisiformis-'Homagnostus fecundus'; and in north-west Siberia between the zones of Maiaspis spinosa-Oidalagnostus trispinifer and Acrocephalella granulosa-Koldiniella prolixa.