Johnson — On Bothrodendron [Ojjclostigma) kiltorkense. 507 



are now found fossilized (autochtonous)' and did not suffer damage, as 

 specimens carried long distances would (alloclitouous). 



Stratigraphical. 



Special interest attaches to the important paper on Bothrodendron written 

 by Potonie in 1901 (17), partly because this writer's views, if accepted, would 

 minimize the value of the superabundance of Bothrodendron remains as con- 

 clusive evidence of the Devonian age of the beds containing them, and 

 partly because the species described at length by Potonie — Cijclmtigma 

 herci/nhim, Weiss — shows a striking parallelism in most of its features, as far 

 as they are knowo,^ to Bothrodendron kiltorkense. Cyclostigma hercynium 

 occurs in the Tanner Grauwaoke of the Harz Mountains. These are strata 

 which are regarded by German geologists as Silurian. In the course of his 

 description of the specimens of G. kiltorkense from Bear Island, Heer points 

 out the closeness of affinity of Roemer's specimen of Sagenaria, from the 

 Harz beds of Lautenberg, to C. kiltorkense. These same specimens are now 

 included by Potonie in the species C. hereijnium, Weiss, so closely allied to, if 

 not identical with, C. kiltorkense. As Heer placed C. kiltorkense in the Ursa 

 stage above the Devonian beds, he would hardly have been prepared to 

 admit that Roemer's Sagenaria (C. hercynium, Weiss) was Silurian. The recent 

 work of Dr. Marie Stopes (18) shows that the Gaspe beds in Eastern Canada, 

 yielding C. densifolium, &c.,^ and assigned by Dawson (19) to the Silurian 

 epoch, are, as long suspected, in reality Devonian. It is difficult to accept 

 tlie view that the Bothodendron flora, which in all those other parts of the 

 world where it occurs predominantly is a typical Devonian, one should be in 

 the Harz Mountains a Silurian one. In no other part of the world do Silurian 

 rocks, recognized as such, yield Bothrodendron remains. The difficulty is not 

 lessened by the fact that the beds grouped as Devonian in the Harz 

 Mountains are almost devoid of plant-remains. Tlie meagre scraps — several of 

 which are figured by Potonie and are Bothrodendron- like — are mostly too 

 poorly preserved for recognition. Even in the Mid-Devonian Flora of 

 Bohemia (Baraude's Silurian H-h) there are no distinct Bothrodendron 

 forms, though certain young Lepidophyte shoots probably belong to Bothro- 

 dendron. There seems no objection, for the present, however, to follow 

 Potonie for correlation purposes, in grouping all the fossil plants found in the 

 Silurian and Devonian rocks together as Pre-Oulmian, so little do true 



I A3 used by Potonie. 



^ C. hercynnim, Weiss, is still known only in the stage with one central scar (leaf-bundle scar 

 in the leaf-scar. 



' 0. densifolium, Daws, has been described as a badly preserved specimen of B. kiltorkense. 



SCIENT. PKOC. E.D.S., VOL. XIII., NO. XXXIV. 4 F 



