Abstract
Kochaspids are an informal group of ptychopariid trilobites that were both abundant and widespread in the early Middle Cambrian of North America. Based on the reassociation of pygidia and cranidia of some kochaspids,KochiellaPoulsen, 1927, is redefined andHadrocephalitesn. gen. is proposed.Hadrocephalitesincludes taxa previously assigned by Rasetti and Palmer toSchistometopusResser, 1938a.Schistometopusis considerednomen dubium.Representatives ofKochiellaandHadrocephalitesfrom the Pioche Shale and Carrara Formation of Nevada are described, including the new speciesKochiella rasettii, K. brevaspis, Hadrocephalites lyndonensis,andH. rhytidodes.Other kochaspids previously assigned toKochaspisResser, 1935;EiffelaspisChang, 1963;Schistometopus;andKochiellaare discussed and some are reassigned. The type specimens ofKochiella augusta(Walcott, 1886);K. crito(Walcott, 1917b);K. chares(Walcott, 1917a);K. mansfieldiResser, 1939;K. arenosaResser, 1939;Hadrocephalites carina(Walcott, 1917b), andH. cecinna(Walcott, 1917b) are re-illustrated.
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