24 T. O. HALLE, LOWER DEVONIAN PLANTS FROM RÖRAGEN IN NORWAY. 



belong to the same kind of plant. In pl. 4, fig. 17, is figured another specimen which is 

 also characterized by repeated bifurcation. It differs from those now described through 

 its smaller size and very slender and delicate branches. A very different habit is pre- 

 sented by the impression shown in pl. 2, fig. 9. It is characterized by a somewhat diffe- 

 rent manner of branching: it evidently divides dichotomously into branches of equal 

 strength, but one of the two sister-branches takes more or less the direction of the part 

 below the bifurcation, so that a sympodium is formed. The thickness of the branches 

 remains the same throughout the whole system of ramifications. This specimen is rather 

 different from other forms referred to Hostimella, and should perhaps not be brought to 

 that provisional genus. 



It is remarkable that among the large number of slender, dichotomously di vided 

 branch-systems of the HostimeUa-type collected at Röragen not one is found to show 

 any trace of laminae. 



Aphyllopteris sp. — Pl. 2, figs. 10—12. 



The provisional generic name Aphyllopteris proposed by Prof. Nathorst may be 

 used as a designation for sterile rachis-like branch-systems, without leaves or pinnules, 

 which do not have the characteristic dichotomic branching of Hostimella. 



The specimens shown in pl. 2, fig. 10, consist of a marked, stout main axis and 

 more slender lateral branches. The habit suggests a fern-rachis, but there is no indica- 

 tion of pinnules. 



The photograph in pl. 2, fig. 11, represents a large slab of slate covered with im- 

 pressions of sj3arsely branching stem-like structures. Tliese have a markedly parallel 

 direction över the whole slab, of which only a part is here figured. The whole arrange- 

 ment suggests soft and slender water-plants all swaying to one side with the current 

 and embedded in that position. In several places the band-like impressions have a distinct 

 central furrow, evidently caused by the presence of a strand of finner texture. This 

 strand is more distinctly seen in fig. 12, which represents some specimens of the same 

 kind. The strand is here replaced by some ferruginous substance and stånds o ut in relief 

 against the flat surface of the band-like impression. 



Dawsonites arcuatus n. gen. et sp. - Pl. 3, figs. 1 — 9; pl. 4, figs. 18—21. 



Psilophyton princeps Davvs. pars, Dawson 1871, p. 37; pl. 9, figs. 102, 103, 105—108; pl. 10, figs. 118, 121? 

 >'Sporanges attribués au Psilophyton princeps», P. Bertrand 1913, p. 160, fig. 2. 



Specimen mentioned by Nathorst 1913, p. 27, pl. 5, fig. 14, as agreeing well with Dawson's sporangia of 

 Psilophyton. 



Historical. 



It has already been remarked by Solms-Laubach (1895) that the supposed frueti- 

 fications referred by Dawson in 1871 to his Psilophyton princeps have not really been 

 proved to belong to that species. The characters of these fruetifications are given by 



