304 ON THE AGE OF THE 



The surface, though entirely destitute of regular ribs or strisB, is 

 marked, especially in the vicinity of the joints, with low, short, 

 triangular plicatures, apparently due to compressing action. At 

 the joints, which are beautifully distinct, and over much of the 

 surface, the slaty matter is covered with a siliceous coating of a 

 lighter color and much greater hardness than the body of the 

 rock, derived a})purcntly from the joints and epidermis of the 

 plant. 



The lower and toothless joint, in Plate XXXI, fig. 3, Sternberg, 

 representing Equisetites aculus, bears a strong resemblance to this 

 fossil, as do also the reed-lilce stems represented along wdth im- 

 pressions of Zamites heterophyllus^ in Plate XLIII, figs. 4 and 5, 

 Sternberg. 



Calamites arenaceus. Brongn. 



The fossil refen-ed to by this title is frequently met with in the 

 coal rocks of Eastern Virginia, occurring both in the dark lami- 

 nated slates, and in the soft, bluish-gray sandstones. In the for- 

 mer position it is generally very much flattened, from compres- 

 sion between the layers of slate ; in the latter it is often quite 

 cylindrical, being found in an erect posture in the roclv. 



On comparing some good specimens in my collection with 

 Brongniart's figures and description of C. arenaceus, I am con- 

 vinced that our fossil is of this species, or one very closely allied 

 to it, and that it differs in many important points from C. Suck- 

 oiciL The calamite from Eastern Virginia, forwarded by Prof. 

 Silliman to M. Brongniart, and by the latter figured as C. Suck- 

 oivii was obviously, and as he himself confesses, a very imper- 

 fect one, and as will be seen by inspecting his dra^^'ings, differs 

 in many respects from the other specimens, referred by him to 

 the same species, all of which were derived from the true car- 

 boniferous formation. From Brongniart's drawing of the Vir- 

 ginia specimen, and his statement that it is nearly or entirely 

 destitute of tubercles at the joints, in which it strikingly differs 

 from the true C Suckowii, and agi-ecs with the arenaceus, I am 

 fully convinced that the fossil figured by him as a variety of C. 



