106 THE MEDALS OF CREATION. Cuap. VI. 
fine specimens have been collected, especially from the vicinity 
of Whitby. In the sandstone of the Inferior Oolite of the 
Cleveland Hills, Yorkshire, numerous stems of this colossal 
marestail have been observed standing erect, as if occupying 
the position in which they grew; the same fact was also 
discovered at Carlton Bank, near Stokesly, forty miles from 
the coast. In both localities fossil shells of fresh-water mus- 
sels (Uniones) were associated with the vegetable remains. 
This plant is a true equi- 
setum, differing chiefly from 
existing species in its gigan- 
tic size and arborescent cha- 
racter. The sheaths sur- 
rounding the stem, and the 
verticillate linear leaves, are 
preserved in some examples: 
Lien. 13. EQUISETITES COLUMNARIS. : 
(Adi Bronte SPOS) and in all, the furrows left 
Lower Oolite. Whitby. by the imprints of the sheaths 
Fig. 1.—Portion of a stem, showing 
two articulations, and an in- 
termediate constriction. 3 nat. 
2.—A few of the denticulations 
produced by the sheath. nat. 
are more or less strongly 
impressed. The stem is not 
channelled throughout, as in 
Calamites, the carboniferous 
plant whose stems at first sight might be mistaken for those 
of Equisetites, but which are entirely distinct, as will be. 
explained hereafter. The Equisetites columnaris is peculiar 
to the Oolite; it does not occur in the coal-measures. 
Specimens have been discovered which indicate a height 
of twenty feet, and a diameter of several inches.* 
A small species of Equisetum (Hq. Brodievt) occurs in 
the insectiferous limestone of the lower Lias, at Strensham, 
Worcestershire, associated with the foliage of fresh-water 
endogenous plants resembling the Potamogeton, or pond- 
weed, and of supposed dicotyledonous vegetables. 
* See Hist. Vég. Fossiles, p. 115. 
+ Prof. Buckman, in Geol. Journal, vol. vi. p. 413. 
