14 T. G. HALLE, LOWER DEVONIAN PLANTS FROM RÖRAGEN IN NORWAY. 



somewhat broacler in the upper part, and they are directed more forward without being 

 falcate. Stur, it is true, mentions that in his specimens the matrix surrounding the 

 impressions has been stained in order to make the outlines appear more distinct, and 

 t his may account for the apparent difference in breadth of the leaves; but there is at 

 any råte not sufficient reason as yet to identify these forms, which are probably iden- 

 tical, with Dawson's species. In the monograph of the Devonian flora of Bohemia by 

 Potonié & Bernard (1904), Lessonia bohemica and Fucus Novaki are ref erred to Psilo- 

 phyton spinosum (Krejci) P. & B. and P. bohemicum (Stur) P. & B. 



In a collection of fossil plants from the province of Szechuan in China made by 

 Mr. V. K. Ting, Director of the Geological Survey of China, I have recently iden- 

 tified a typical specimen of Arthrostigma gracile showing the central strand verv 

 distinctly. 



Finally it may be mentioned that Stur (1875 — 1877) has fignred under the name 

 of Hymenophylhim ivaldenburgense a specimen which at any råte has a certain super- 

 ficial resemblance to Arthrostigma both in regard to the general habit and through the 

 occurrence of what appears to be a single central vascular strand. 



Psilophyton princeps Daws. (pars). - - Pl. 1, figs. 21—31; pl. 2, figs 1 — 5; pl. 4, 



figs. 6— 14 b. 



? Branched root, Salter 1858, p. 77; pl. 5, fig. 5. 



Psilophyton princeps, pars, Dawson 1859, p. 478; fig. 1, pars (1 a — 1 d, 1 f — h?). 



Psilophyton princeps Daws. and var. ornatum Daws., pars, Dawson 1871, p. 37; pl 9 (with the exception of 



figs- 102, 103, 105—108) 

 ? Cyclostigma densijolium Daws., Dawson 1871, p. 43; pl. 8, figs. 92 (?), 93—96. 

 ? Psilophyton grandis, Penhallow 1893, p. 113; pl. 12, fig. 12 a; pls. 13, 14. 

 Psilophyton princeps Daws., P. Bertrand 1913, p. 159, fig. 1. 

 Cfr. Psilophyton, Nathorst 1913, p. 27; pl. 5, figs. 12, 13. 

 Psilophyton sp., Nathorst 1914, p. 29, pl. 8. 



Historical. 



The species Psilophyton princeps Daws., which is represented at Röragen by a 

 large number of specimens, was instituted by Dawson in 1859. This species should be 

 regarded as the typical representative of the much discussed genus Psilophyton, the true 

 nature of which is still a matter for dispute. Under the name of Psilophyton have been 

 brought together a great number of very heterogeneous and doubtful objects, and it will 

 be necessary to establish some kind of understanding regarding the use of this generic 

 name. Solms-Laubach has given in 1895 a very lucid exposé of the more important 

 facts published up to that date on the different forms of Psilophyton, but he doesnot pro- 

 pose any definite classification of the various remains referred by different authors to 

 this genus. Since then, D. White (1905, p. 58) has given a splendid critical summary 

 of the most important facts relating to Psilophyton princeps, partly based on a reexa- 



