Abstract

Trilobites previously assigned to the Entomaspididae Ulrich inBridge, 1931 are common in Laurentian strata assigned to the upper Sunwaptan Stage of the Upper Cambrian. Most species are poorly known, and typically only sparse cranidial data are available. Large silicified samples from the Lava Dam Member of the Notch Peak Formation, western Utah, contain three new species for which cranidia, librigenae, thoracic segments, and pygidia are known. The species permit clarification of the morphology and affinities of previously described taxa from elsewhere. They are referred to Notchpeakia n. gen. (type species: N. milleri n. sp.) which, in addition to the type includes N. taylori n. sp., N. notchpeakensis n. sp., N. cherrycreekensis n. sp., and N. varga (Westrop, 1986). The “entomaspidid” trilobites are assigned to the traditionally post-Cambrian Harpetidae Hawle and Corda, 1847.

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