DESCRIPTION OF SPECIES. 13 



stems, the smaller dimensions of the sheath, and the lesser number of the 

 teeth and ribs. The ribs also are not flat, do not narrow in the same way 

 to form the teeth, and above all do not have any deciduous process at the 

 end of the teeth. Bronn, in " Lethaea Geognostica," plate xii, fig 3, gives 

 a representation of a plant from the " Lettenkohle " of the Keuper, which 

 is very much like our plant. He calls this Equisetites columnarls, but 

 Schimper argues, I think correctly, against the occurrence of E. columnare 

 in the Keuper. At the same time this plant of Bronn seems to be quite 

 different from E. arenaceum, as figured by all the authors, and especially by 

 Heer, who has given excellent figures of this plant as found in the Keuper 

 of Switzerland. 



Perhaps Bronn's Equisetum may be the E. mytharum of Heer, which 

 occurs in the Lettenkohle of Switzerland. At any rate this is the Triassic 

 Equisetum that is nearest to our plant. 



Schimper, in describing the plants from the Richmond Coal Field, has 

 made the mistake of placing plants from the same strata in very different 

 geological formations. Thus he places E. Bogersi in the lower "Marnes 

 irisees" of Blackheath, near Richmond, Va., while he places its constant 

 companion, Macrotozniopteris magnifolia, in the Oolitic strata of Richmond 

 in Virginia. He places Neuropteris linncecefolia, also in the Oolitic beds of 

 Richmond, although this plant, too, occurs in the same localities with E. 

 Bogersi. 



Formation and locality. — Everywhere in the Richmond Area, from the 

 horizon of the coal beds to the highest beds of the area. 



Equisetum arundiuiforme, Rogers. 



I have seen impressions of this plant as described by Prof. William B. 

 Rogers in his paper on the "Age of the Coal Rocks of Eastern Virginia," 

 published in the "Transactions of the Association of American Geologists 

 and Naturalists." I am strongly inclined to think that they are casts of the 

 young stems of E. Bogersi. There may be a second Equisetum in the 

 Richmond Coal Field, as the internal casts called Calamites sometimes vary 

 a good deal, but until an impression of the outer surface of a plant different 

 from E. Bociersi is found, and while we do not know the limits of variation 



