234 



Reports and Proceedings- 



lagoons from decomposing vegetable matter, meeting with protoxide of iron in 

 solution, would unite with it to form carbonate of iron, which, with the mud of the 

 lagoon, would produce Clay-ironstone, Thus, in the author's opinion, the beds of 

 Clay-ironstone, like Coal-beds, mark terrestrial horizons. The author supported his 

 views by reference to various sections, and also cited the occurrence of what he re- 

 garded as an analogous phenomenon on a small scale in some mud obtained from the 

 shore between Redcar and Saltburn. 



Discussion. — Prof Ansted thought that the explanation offered by the author, 

 though satisfactory for instances of limited thickness and confined area, was not 

 equally applicable to the far larger deposits, such as those in America, extending over 

 hundreds of square miles, and many times as thick as those described. The beds had 

 by some been considered as due to segregation subsequently to deposition ; but this 

 view also seemed hardly such as could be generally accepted. The deposits of iron- 

 stone varied much in character, sometimes consisting of layers of distinct nodules, 

 sometimes of continuous bands. The origin of these two classes appeared to him to 

 ha-v'e been different, and in some of the Coal-deposits the ironstone bands were present 

 on a more extended scale than seemed consistent with the author's theory. 



Prof. Eamsay thought that the paper exhibited considerable ingenuity, and that 

 the examples given by the author were intended by him to be equally applicable to 

 large areas. The estuarine character of much of the Coal-deposits was an ac- 

 knowledged fact; and the theory proposed by the author was quite in accordance 

 with such a state of things. He did not agree with him that ironstone was never 

 deposited in marine strata, as it occurred in the Yoredale beds and in some Liassic 

 beds. As to the deposits of ironstone in freshwater, he referred to those still taking 

 place in some of the Swedish lakes. 



Mr. Forbes, whilst admitting that in many instances Clay-ironstones had been 

 deposited in circumscribed waters or shallow lakes, as is the case with the lake iron- 

 ores in Sweden now actually in process of formation, pointed out that some of the 

 largest Clay-ironstone deposits in England, those of the Yoredale series, contained 

 marine fossils in abundance. On chemical grounds it is not clear in what state of 

 combination the author imagines the iron to be held in solution previous to having 

 been, according to him, converted into carbonate of iron, by meeting with the 

 carbonic acid formed in the lagoons from decomposing vegetable matter; and further, 

 the mere fact that the Saltburn mud eifervesced with nitric acid after having been . 

 bottled for some days, must not be regarded as necessarily proving the formation of 

 carbonate of iron in it. 



Mr. Charlesworth called attention to the nodules of ironstone which were found in the 

 coprolite diggings in Suffolk, as to the origin of which little was known. The banding 

 in the interior of these nodules was posterior to their formation, as was evinced by 

 its following the contours of the exterior, and even of lithodomous borings in them. 



4. " Note in vindication of Leptophlceum rhombicum and Lepidodendron Gas- 

 pianum." By Principal Dawson, LL.D., F.R.S., F.G.S. 



This note accompanied some photographs of the remains of plants referred to, and 

 was in opposition to the identification of these remains with the Lepidodendron 

 nothum, Unger, as proposed by Mr. Carrutbers in his Appendix to Mr. Daintree's 

 paper on the Geology of Queensland (Q. J. G. S. 1872, vol. xxviii., p. 350). The 

 author maintained that his Lejndodendron Gaspianum is distinct from Unger's species, 

 although nearly allied to it, and that his Lcptophloeum rhombicum differs from both 

 generically and specifically. He tabulated as follows the characters of his two species : — 





Lepidodendron Gaspianum. 



Leptophloeum rhombicum. 



Stems and branches... 

 Vascular scars 



Long and slender; areoles 

 elongate lanceolate. 



In middle of areole or nearer 

 upper end, according to the 

 surface exposed. 



Short and much curved out- 

 ward. 



Small, scaly. 



Unknown ; probably allied 

 to Carboniferous Lepido- 

 dendra. 



Short and stout; areoles 

 regularly or transversely 

 rhombic. 



Always in middle of areole. 



Long and somewhat straight 



and erect. 

 Long, leafy. 

 Known to possess a large 



Stcrnbcrgia-\)\t\\, and to 



have a very thin cortical : 



layer. 



Leaves 



Fruit 



Structure 





