The studies on which the following somewhat epitomized discussion is based were prosecuted with the purpose of ascertaining, so far as the available data will permit, the comparative age of the basal coals of the Lower Coal Measures of Henry county, Missouri, and their approximate stage in sections of the Mesocarboniferous in other typical areas. The materials used are taken from a more extended work on the floras of the Lower Coal Measures of Missouri, in which the systematic treatment of the species involved in the present problem will be found.

The plants so abundantly gathered from the lower coals of this region may be regarded as typical of this zone in the trans-Mississippi area;

and, since the Lower Productive Coal Measures of the more eastern states is, paleobotanically, by far the best known portion of the sections, the material in hand is better adapted to immediate correlative comparisons . . .

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