Article: Lower and early Middle Cambrian trilobites from the Pioche Shale, east-central Nevada, U.S.A.
Trilobites belonging to the Upper Olenellus Faunizone (Lower Cambrian) and to the late Albertella and Glossopleura Faunizones (Middle Cambrian) are described from a single stratigraphic section that spans the Pioche Shale. Trilobites representing the oldest Middle Cambrian, the Plagiura-Poliella Faunizone, and the early Albertella Faunizone were not found. The interval in which the latter trilobites might be expected contains 260 ft. of barren strata. Four established, two undetermined, and three new species are described from the Upper Olenellus Faunizone. Fourteen established, five undetermined, and seventeen new species are described from the late Albertella Faunizone and Glossopleura Faunizone. Some of these latter species are placed in two new genera, Achlysopsis and Albertelloides. Seven undetermined and seven new species are described from the Glossopleura Faunizone.The Pioche Shale is locally 1,280 ft. thick and is exposed in an 8,800-ft. section containing Lower, Middle, and Upper Cambrian strata.