22 



T. G. HALLE, LOWER DEVONIAN PI.ANTS FROM RÖRAGEN IN NORWAV. 



as to rencler it necessary to institute a new species. It 

 lias been proposed, however, above to use the name 

 Psilophyton princeps in a somewhat narrow sense: to that 

 species should be referred only forms agreeing with those 

 of Dawson's specimens which alone are sufficiently well 

 characterized to serve as types for the species, viz., those 

 figured in Dawson's Report of 1871, pl. 9, figs. 97 — 101, 

 104, 109, 110. Psilophyton princeps, as so defined, has 

 a manner of branching quite different from that of the 

 specimen which has been made the type of P. Gold- 

 schmidtii and others similar to it. In P. Goldschmidtii 

 there is a differentiation of lateral branch-systems which 

 divide in a manner quite distinct from that of the main 

 axis. These lateral branch-systems ha ve a very different, 

 spreading habit because of the wide angles of the bif ur- 

 cations, which are repeated at short intervals. They 

 give the impression of being spread out in one plane and 

 in their general aspect on the whole recall the ramifica- 

 tions of a large dichotomously divided frond, though 

 there are no traces of any laminae. 



Isolated branch-systems similar to those arising 

 from the main axis of the type -specimen are very com- 

 mon both at Röragen and in other Devonian plant-bearing 

 deposits. Specimens of that kind were included by Daw- 

 son in his Psilophyton princeps and are still of ten described 

 under that name. In order to establish an acceptable de- 

 finition of the genus Psilophyton, it is necessary to confine its use to stem-like structures 

 bearing spines or small leaves, as proposed above. Isolated branch-systems without spines, 

 like those here discussed, may equally well represent branches of the rachis of a frond 

 and cannot be regarded as belonging to Psilophyton unless they are found in actual connec- 

 tion with spine-bearing Psilophyton-stems or there is some other special reason to believe 

 that they belong to them. They should in that case be referred to Psilophyton Gold- 

 schmidtii and not to P. princeps, which species, as set forth above, has a different 

 manner of branching. 



Specimens consisting only of dichotomously divided branch-systems, if they are 

 described at all, should be referred to the provisional genus Hostimella Barr. emend., 

 as employed by Potonié & Bernard (1904, p. 14 and föll.). The numerous specimens 

 of this kind found in the Röragen deposits are therefore not here included in Psilophyton 

 Goldschmidtii, though it is probable that some of them may have been borne by stems 

 of the Psilophyton-type. One of these specimens, however, presents such a close resem- 

 blance to the type-specimen of P. Goldschmidtii that the specific identity is very prob- 

 able in spite of the absence of the proof of actual connection. This is the specimen 

 shown in pl. 2, fig. 7. It is more complete than the lateral branches of the type-specimen 



Fig. 2. — Psilophyton Goldschmidtii n sp. 



— After Nathorst, 1913, pl. 3, fig. 3. 



Natural size. 



