Middle Cambrian trilobites from the Ekspedition Brae Formation of North Greenland, with a reappraisal of the genus Elrathina

The richly fossiliferous Ekspedition Brae Formation of North Greenland yields a typical oligospecific fossil assemblage with well-preserved trilobites, helcionelloids, and lingulate brachiopods. The trilobites include Itagnostus subhastatus new species, Itagnostus sp. cf. I. gaspensis (Rasetti, 1948), Elrathina aphrodite new species, Elrathina athena new species, Elrathina hera new species, and Elrathia groenlandica new species-a fossil assemblage typical of the Bathyuriscus-Elrathina Zone as known from the Cordilleran regions of Laurentia. Excellent preservation allows a detailed assessment of the prosopon and elucidates aspects of the ontogenetic development of Elrathina and Elrathia. An evaluation of Elrathina includes a redescription of its type species, E. cordillerae (Rominger, 1887), based on the type material, and indicates that most specimens collected from the Burgess Shale and previously dealt with as E. cordillerae represent a new species.