12 THE OLDER MESOZOIC FLORA OF VIRGINIA. 



tened stem, showing the epidermis which is finely striated and marked by 

 rather large, prominent ribs which cross the diaphragms with no change of 

 direction. No indications of a sheath are to be seen. As it is found with 

 E. Bogersi, I consider it to be the rhizome of this plant. 



This plant is one of the most characteristic fossils of the Richmond 

 Coal Field, and has a wide vertical and horizontal range. I have found it in 

 the Cumberland Area, and everywhere in the Richmond Area where plants 

 occur. It is to be found in the highest strata of the Hanover Area which 

 show fossil plants. It is noteworthy that it is almost everywhere found 

 with Macrotceniopteris magnifolia. The association of the two is so constant 

 that these plants would appear to have grown in close proximity to each 

 other, for I do not think that this association could be explained by any 

 similar peculiarity in their mode of preservation. Together with the Macro- 

 tseniopteris it often forms the only fossil of some localities. It is more 

 commonly preserved in the form of a cast of the interior, known as Cala- 

 mites, and described by several writers as C. arenaceus. I have seen no true 

 Calamites in this coal-field; all the impressions appearing as such are casts 

 of this Equisetum or of some Schizoneura. I was at one time strongly in- 

 clined to consider this plant identical with Equisetum columnare, which it 

 resembles very closely. Prof. William B. Rogers, after a comparison of it 

 with the figures given in Murchison's Memoir on the Brora Coal Field, was 

 very positive in identifying it with the plant there described as E. columnare. 



I have examined the figures accompanying this memoir, and do not 

 think that they show enough characters to permit identification with our 

 plant. The keeled ridges in the figures of Murchison's Memoir certainly 

 strongly resemble those on E. Bogersi. I am now of the opinion that the 

 Richmond plant is a distinct species, perhaps the representative of E. col- 

 umnare. It should retain the name given it by Schimper, viz., Equisetum 

 Bogersi. It does not seem to be identical with any of the figures of E. col- 

 umnare which I have seen. Phillips, in the " Geology of Yorkshire," 3d 

 edition, fig. 4, p. 197, gives a figure of E. columnare, which resembles what 

 would be seen in our plant if the teeth were removed by maceration, and 

 only the ribs with then' converging raised lines were preserved. Our plant 

 is quite different from E. arenaceum of the Keuper in the smaller size of the 



