302 ON THE AGE OV THE 



Fossil Plants of the Oolite Coal Rocks of Eastern 



Virginia. 



Equisetum columnare. Brongn. 



Oncj/logvnalinn carhonarium. Koenig. 



Eqaiselites coliimnaris. Sternberg. 



The fossil referred to under this title, occurs very abundantly 

 in certain slaty and argillaceous rocks met with at nearly all the 

 openings in the coal-fields, both north and south of the James 

 river, and appears to have formed one of the chief sources of the 

 material of the coal beds. The specimens in the slaty rock are 

 generally flattened out parallel with the laminae of the slate, and 

 from the conversion of the vegetable matter into coal, give rise 

 to alternations of coal and slaty material, sometimes as numerous 

 as thkty in an inch. On one of these masses of slate in my col- 

 lection, there is a beautiful impression of a part of the Equisetwn, 

 about fifteen inches long, and where widest, seven inches broad, 

 comprising ten distinct articulations, the intervals of which regu- 

 larly diminish from one exti'emity of the fossil to the other. Spec- 

 imens of tills fossil are also met with in a dark bituminous clay, 

 and a light brownish, soft sandstone, both of which occupy a 

 place near tlie coal. In these the rotundity of the stems is pretty 

 well preserved, the rocks imbedding them being destitute of the 

 laminated structure. 



The flattened as well as the convex impressions agree exactly 

 with the figures appended to Murchison's Memoir on the coal 

 field of Brora, Trans. Geol. Soc. of Lond., Vol. II, Part II, and 

 correspond in every particular with the description of the Brora 

 fossil as given by Koenig in this memoir. The " acute regular 

 furrows of various lengths, gradually diminishing in width, and 

 running out into linear grooves," and "the elevated rays or ribs 

 having a pretty acute ridge, and gi-adually tapering into a fine, 

 more or less lengthened raised line," refeiTcd to by Koenig, as 

 impressions produced by the flattened stem of the Oncylogonatum ^ 

 and represented in figures 3 and 4, of Mr. IMurchison's Memoir, 

 are facsimiles of the Virginia fossil, as it occm-s in innumerable 



