APPENDIX. 271 



similar to those of the underlying beds, though with some species 

 which extend upward into the Millstone Grit. In Scotland the alga 

 named SpiropJm/ton and ArcluBocalamiies radiatua — which in Amer- 

 ica are Krian — appear in this formation. 



(5) The Lower Carboniferous Sub-Flora : 



This group of plants is best seen in the shales of the Horton 

 series, under the Lower Carboniferous marine limestones. It is 

 small and peculiar. The most characteristic species are the follow- 

 ing: 



Dadoxylon (PalcBOxylon) antiquiits, Dn. — A species with large 

 medullary rays of three or more series of cells. 



Lepidodendron corrugatwm, Dn. — A species closely allied to L. 

 VeltJieimicmum of Europe, and which is its American representative. 

 This is perhaps the most characteristic plant of the formation. It 

 is very abundant, and presents very protean appearances, in its old 

 stems, branches, twigs, and Knorria forms. It had well-character- 

 ised stigmaria roots, and constitutes the oldest erect forest known in 

 Nova Scotia. 



Lepidodendron tetragonv/m, Sternberg. 



L. obovatum, Sternb. 



L. aculeatum, Sternb. 



L. dichotomum, Sternb. 



The four species last mentioned are comparatively rare, and the 

 specimens are usually too imperfect to render their identification 

 certain, but Lepidodendra are especially characteristic trees of this 

 horizon. 



Cyclopteris (Aneimites) Acadica, Dn. — A very characteristic fern, 

 allied in the form of its fronds to C tenui folia of Qoeppert, to C. 

 nana of Eichwald, and to AdiantHea antiquus of Stur. Its f ractifl- 

 cation, however, is nearer to that of Aneimia than to that of Adi- 

 antum. 



Ferns of the genera Cardiopteris and Hymenophyllites also occur, 

 though rarely. 



Ptilophyton plwmula, Dn. — This is the latest appearance of this 

 Brian genus, which also occurs in the Lower Carboniferous of Eu- 

 rope and of the United States. 



Cordaitea borassifolia, Brongt. 



On the whole, this small flora is markedly distinct from that of 

 the Millstone Grit and true coal-formation, from which it is sepa- 

 rated by the.great length of- time required for the deposition of the 

 marine limestones and their associated beds, in which no land-plants 



