14 THE OLDER MESOZOIC FLORA OF VIRGINIA. 



in the appearance of the casts of the interior of this plant, it would be 

 unsafe to establish new species on the variations of such casts so far as 

 as they have been seen. 



Calamites arenaceus, Brongt. 



These casts of the interior of JE7. Bogersi occur in immense num- 

 bers in the shales and sandstones between and immediately over the coal 

 beds, and even in the coal itself. In the shales they are pressed perfectly 

 flat. In the sandstones they are usually crushed more or less, but are not 

 so flat as in the shales. Sometimes in the sandstones they retain their 

 cylindrical shape perfectly. Sometimes in the roof of the main coal seam 

 sandstone casts of Equisetum occur, which rise perpendicular to the top of 

 the seam to a greater or less height. When the impressions are best pre- 

 served, as they are in the fine-grained dark shales, they appear as flat rib- 

 bon-shaped markings, often 10 to 12 centimeters wide, tapering gradually 

 and marked at intervals by constrictions corresponding to the imprints of 

 the diaphragms. Their surface is marked by fine, closely-placed parallel 

 strise, or ribs, which in passing across the constrictions are slightly bent out 

 of their course. 



Formation and locality. — Universally distributed at and above the hori- 

 zon of the coal seams. 



SCHIZONEURA, Schimp. 



Schizoneura planicostata. 



Plate I, Fig. 1. 

 Calamites planicostatus, Rogers. 



The fossils which are supposed to belong here have the form of either 

 flattened or cylindrical casts of the interior of the stem. Their character 

 is as follows : Stem very large, diameter near the base, 17 centimeters and 

 over, internodes of the middle portions of the stem, 17 centimeters long, as 

 seen on flattened specimens ; those of the lower part of the stem were seen 

 only on cylindrical sandstone casts not well marked, but apparently are 7 

 to 9 centimeters long. Eibs 1 millimeter wide, and sometimes a little over, 

 semi-cylindrical, prominent, closely placed, and striate. 



The figure gives a representation of a large flattened cast, which is 

 very perfectly preserved on a fine-grained shale. 



