PTYCHAGNOSTUS Jaekel, 1909. Ptychagnostus richmondensis (Walcott) (xl6), Marjum Formation, M. Cambrian, mouth of Antelope Springs Canyon, Millard County, Utah. (Collected by Afton Fawcett. RLS coll., id., now at FMNH.) Specimen whitened with magnesium oxide. The radiating ornamentation of the cephalon is attributed to alimentary diverticula.
Ptycbagnostus richmondemis (Walcott) (x6.1), Wheeler Shale, M. Cambrian, Antelope Springs, Millard County, Utah. (Collected by Afton Fawcett. RLS coll., id., now at FMNH.)
Several specimens show axial spine on second thoracic segment. The surface features emphasized in plate 116 are very difficult to observe without whitening.
(Matthew), M. Cambrian, Paradoxides da vidis b e d s, Manuels, Newfoundland (x9). (RLS coll., id.)
Family Spinagnostidae Howell, 1935
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