A fossil specimen of the rootlike organ of a plant of the Stigmaria ficoides type was found near the base of the Bird Spring Formation, in a section identified as being Chesterian in age on the basis of megafossils in overlying limestones, in Clark County, Nevada. It proves the existence in the West during Late Mississippian time of arborescent lycopods like those that flourished in the eastern U. S. during the Pennsylvanian. It is not certain whether the siltstone containing the fossil was of marine or nonmarine origin.

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