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Keywords from Image Description:
Walcott Cambrian Geology and Paleontology II plate . Plate Middle Cambrian Trilobita and Merostomata Neolenus and Sidneyia Neolenus serratus Rominger Rominger Walcott Charles Walcott Middle Cambrian Merostomata Smithsonian Miscellaneous Collections Volume Number Publication City of Washington Published by the Smithsonian