Abstract

Agnostoid trilobites are abundant and diverse in 10 collections from the Henson Gletscher and Kap Stanton formations of North Greenland. Three agnostoid assemblages are identified from slope apron to deep outer shelf lithofacies, representing the Ptychagnostus gibbus, Ptychagnostus atavus, and lower Lejopyge laevigata intervalzones ofMiddle Cambrian age. This is the first report offossils from the P. atavus Zone in Greenland.

At least 17 agnostoid genera are represented in the Henson Gletscher and Kap Stanton formations, of which Megagnostus and Schismagnostus are new. Diagnoses of Agnostus, Diplorrhina, Doryagnostus, Lejopyge, Peratagnostus, Peronopsis, Pseudophalacroma, and Tomagnostus are emended. From review of type material, slome of which is illustrated with new photographs, Cyclopagnostus, Grandagnostus, Phoidagnostus, Quadragnostus, and Spinagnostus are considered to be unrecognisable genera.

FortY agnostoid species, some in open nomenclature, are identified from the new collections. The species Agnostus lophotus, Diplorrhina oncota, Megagnostus diclidus, Schismagnostus plicatus, and Tomagnostus bothrus are new. Abrupt early holaspid metamorphosis occurred in the cephalon of Schismagnostus plicatus and in the pygidium of Peratagnostus cicer. A lectotype is selected for Agnostus lens Gronwall, 1902, which is the type species of Cotalagnostus.