28 EQUISETITES. 
Type. Pieces of stem with well-marked dentate sheaths. The 
species is thus defined by Dunker: ‘‘ Lquisetites caule tenui multi- 
articulato, striato, striis subacutis viiii—x. aeque distantibus, vaginis 
tumidis lanceolato-dentatis.”’ 
The specimen figured by Dunker has much shorter internodes 
and more distinct sheathing leaves than most of the English 
examples. Schenk’s figures afford a much better idea of the 
species as represented in the National Collection; long slender 
internodes with tubers attached to the nodes. The characters 
shown in Dunker’s figures are those of subaerial branches, but most 
of Schenk’s specimens are underground stem structures. 
Lquisetites Burchardti, Dunk., is chiefly conspicuous by the 
tubers which occur in large numbers, both isolated and attached 
to the stem. The oval bodies figured by Stokes and Webb under 
the name Carpolithus Mantelli have been included by later writers 
under Dunker’s species. In the above list of synonyms I have 
given expression to a feeling of uncertainty as to the correctness of 
this view ; the enlarged drawing given by Stokes and Webb! shows 
certain characters suggestive of something quite distinct from an 
Equisetaceous tuber. If their figure be an accurate representation 
of the fossil, its true position must be regarded as somewhat 
doubtful. The other species of Carpolithus figured by Dunker 
are referred to Eguwisetites Burchardti, with the exception of 
Carpolithus sertum,* which is probably identical with 4. Yokoyama, 
sp. nov., and C. Brongniarti,® which represents a tuber much larger 
than #. Burchardti, and somewhat different inform. In the figures 
of C. cordatus the slightly cordate tuber is attached to a node of 
the slender stem of #. Burchardti. Dunker’s various species of 
Carpolithus were transferred by Schimper to the genus Cycadino- 
carpus, indicative of Cycadean affinities. In 1871 Schenk figured 
some examples of Lquisetites Burchardti, which showed conclusively 
the true nature of most of the various forms of tubers previously 
classed with fossil fruits. He pointed out how the variations in 
size and shape, as represented in Dunker’s figures, could be easily 
explained by the effects of pressure and the manner of preservation. 
If we examine these figures carefully it appears improbable that 
1 Loe. cit. pl. xlvii. fig. 1. 
? Wealdenbildung, p. 22, pl. vii. fig. 3. 
3 Ibid. p. 22, pl. ii. figs. 6 and 6a. 
