ERDTMAN, TWO NEW SPECIES OF MESOZOIC EQUISETALES. 3 



E. Münsteri Sternb., which is not among the largest species 

 of the genus. Only irl one case have internodes of the length 

 of 6 cm been measured; the ordinary length seems to be 

 4 — 5 cm, with the exception of shoots not quite grown to 

 full size on which internodes measuring only 2 — 3 cm in 

 length have been found. As appears from the figures (1,2, 

 4, 5), the impressions of the stem show a distinct striation. 

 The internodes would thus seem to have been provided with 

 distinct furrows (=^ the ridges on the impressions), which is 

 one of the differences between this species and the one that 

 is probably most closely related: E. Mohergii Moll. The 

 nodes have the same thickness as the internodes; the few 

 diaphragms which are to be found in the material are in a 

 very bad state of preservation. 



Fig. 8 shows the impression of a spore-bearing cone and 

 fig. 6 probably a rhizome-impression, differing from the im- 

 pressions of the aerial stems through the rough and more 

 irregularly striated surface. A tuber is shown in fig. 7. 

 Fig. 2 (VO gives a good idea of the form of the leaf- teeth, 

 as shown by the impression, and fig. 4 shows the carbonized 

 substance of the leaf-teeth. It is worthy of remark that 

 the number of the teeth is the same as the number of the 

 furrows of the stem, which is also the case with the recent 

 Equiselacece. The present species is the first one of the genus 

 Eqiiisetites in which this case has been stated. 



The two species to which E. intermedius appears to be 

 most closely related are E. Münsteri Sternb. (Rhaetic) and 

 E. Mohergii Moll. (Liassic or younger, KurremöUa in Scania). 

 E. Münsteri is the largest of these three species. The breadth 

 of the stem is here 10—15 mm on the impressions, or some- 

 times even more than 20 mm. The stem of E. iritermedius 

 measures 8 mm (4 — 12 mm) and that of E. Mohergii 4 — 7 mm 

 in breadth. The number of the leaf-teeth of the three species 

 is, as it were, inversely proportional to the breadth of the 

 stem; the one with the narrowest stems — E. Mohergii — 

 has 16—20 leaf -teeth, E. intermedius 16 (12—18) and E. 

 Münsteri 12 (10—14). E. il/ww5<en has the thickest and most 

 distinctly furrowed internodes; those oi E. Mohergii are very 

 slender, very little or not at all furrowed, and measure at 

 most 8 cm in length. E. intermedius is intermediate in these 

 respects, with narrow, distinctly furrowed internodes, whose 



