28 EQUISETITES. 



Type. Pieces of stem with well-marked dentate sheaths. The 

 species is thus defined by Dunker: " Equisetites caule tenui multi- 

 art iculato, striato, striis subacutis viii.-x. aeque distantibus, vayinis 

 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. 



Equisetites 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 Equisetites Burchardti, with the exception of 

 Carpolithus sertum? which is probably identical with E. Yokoyamce, 

 sp. nov., and C. Brongniarti? which represents a tuber much larger 

 than E. Burchardti, and somewhat different in form. In the figures 

 of C. cordatus the slightly cordate tuber is attached to a node of 

 the slender stem of E. 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 Equisetites 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 Loc. cit. pi. xlvii. fig. 1. 



2 Wealdenbildung, p. 22, pi. vii. fig. 3. 



3 Ibid. p. 22, pi. ii. figs. 6 and 6a. 



