Johnson — On Bolhrodendron {Cyclostigma) kiltorkense. 511 



marked external features, as the pliotograph shows, which are usually 

 associated with a Calamite. Although tlie Sphenopliyllales and Pseudoborniales 

 are found in the Devonian rocks, the genus Asterocalamites, the earliest of the 

 Equisetacese or Calamarife, the other group of the Articulatse, is not found, 

 according to Potonie, in rocks (records notwithstanding) earlier than the Culm 

 or lowest Carboniferous. Bothrodendron is the earliest of the Lepidopliytes, 

 and in its calamitoid characters brings us nearer to the ancestral group of 

 Pteridophytes common to the Lejpidophyta and Articulatse, to a group 

 suggested by Scott (20) in the course of his description of the complex cone 

 of Cheirostrobus. Nathorst, writing in 1894 (and in 1902, op. cit., p. 33), 

 regrets that neither the modes of branching, the cones, leaves, nor roots of 

 such an important genus as Botlirodendron are known, since it is from it 

 perhaps that Lepidodendron and Sigillaria are derived, he states. 



Knorria Stage. 



One of the most important features of Potonie's account of C. herci/nhim 

 is the description and identification of the numerous Knorria species of earlier 

 publications as states of preservation of C. hercynmm. Knorria is a decorticated 

 stem showing the petrified parichnos-strand of various forms indicated by the 

 specific names employed. In the strand towards its upper end there may be 

 often found a groove or slit representing the leaf-bundle scar surrounded by 

 the parichnos-strand. This is well seen in Knorria acicularis. In this 

 connection the Kiltorcan stem figured (Plate XLI, figs. 1 and 2) is of interest. 

 It is clearly in the Knorria acicularis stage. The epidermis and cortex have 

 disappeared, and tlie more or less fusiform petrified parichnos-strand is 

 evident, with the characteristic slit-like bundle-scar enclosed at the upper end. 

 (Compare Potonie's fig. 28, p. 63 : Die Silur-Flora.) The comparison 

 strengthens the impression that C. hercijnium differs little, as far as known, 

 if at all, from B. kiltorkense. Even the Knorria Selloi stage (Potonie, fig. 20, 

 p. 45) of C liercijnimn occurs in Kiltorcan material (Plate XXXVIII, fig. 3). 

 As Knorria stages are in some deposits the only ones found, their strati- 

 graphical value is naturally increased by their correct identification with 

 known species of recognized genera. It is the more necessary to mention 

 them here, as Heer emphasizes the absence of a Knorria stage in Cyclostigma 

 as a feature of distinction of this genus from Lepidodendron. 



There are several Knorria specimens of Bothrodendron hittorkense from 

 Co. Cork in the Collections of the Geological Survey of Ireland. One of these 

 (" Knorria : Carboniferous Slate, Cork, west of Shehybeg Mountain ") is a 

 petrification showing a typical Knorria Selloi stage. The parichnos-strands 

 are broad and truncate. Another specimen (4974, from the Old Red Sand- 



