Palaeontoloffie. 403 



'& 



an 'Roof-Nodules' of the European Carbonilerous. (Quart. 

 Journ. Geol. Soc. LXV. p. 195—205. 9 pl. London, 1909.) 



This paper contains an account of nodules of Cretaceous age 

 obtained by the author in the north of Japan. They are of interest 

 principally because of the petrifactions of plants which they contain, 

 which are of a t)'^pe hitherto unknown from the Mesozoic. 



The present paper gives an account of the geological details of 

 the formation and structure of the nodules. They are contrasted 

 with the 'Goal- and Roof-nodules' of the English seams (which have 

 yielded the well known plant petrifactions) and are shown to have 

 some of the characters of each. The nodules were formed near to 

 the shore, and contain marine Shells with tangled debris of plant 

 remains, which are sometimes very minute. The nodules are not 

 directl}^ connected with any coal seams, but lie in a thick series of 

 shales below the coals. In microscopic section the matrix appears 

 highly granulär, unlike the matrix of coal-balls and roof-nodules. 

 Their chemical composition is roughly 60°/o carbonates, and 30% Sili- 

 cates. In having numerous plant fragments in a Single nodule and 

 in the type of petrifaction, the nodules are like 'coal-balls', and in 

 having marine Shells included in the matrix, they are like 'roof- 

 nodules'. M. C. Stopes. 



Stopes, M. C. and D. M. S. Watson. On the present Distri- 

 bution and Origin of the calcareous Concretions in 

 Coal Seams. known as "Coal Balls". (Phil. Trans. Roy. Soc, 

 Ser. B. Vol. 200. p. 167 - -218. 3 pl. and 7 text-figs. 1908.) 



This paper deals primarily with the plant-containing, calcareous 

 nodules or "coal balls" and their relation to the beds in which they 

 occur. After an introductory historical section the authors give a 

 füll account of the results of their investigation into the occurrence 

 of the "coal balls". These support the conclusion that the "coal balls" 

 were formed as concretions in the seams in which they are now 

 found and have not been derived from other sources. In this con- 

 nection considerable importance attaches to the discovery of several 

 cases in which the same stem is conti nued through two or more 

 adjacent nodules. The third section of the paper deals with the 

 geological horizons of the beds containing the "coal balls". It is 

 shown that their occurrence is not restricted to a single seam in 

 the Lower Coal-measures as is commonly supposed. The chemical 

 composition and formation of the "coal balls" is considered in the 

 fourth section. Numerous analyses are given which show a high 

 degree of variability in the relative amounts of calcium and magne- 

 sium carbonates — of which the "coal balls" principally consist. These 

 petrifying agents are supposed to have originated from the calcium 

 and magnesium sulphates of the sea water. No fact in the course 

 of their work has impressed the authors more than the influence of 

 sea water on the formation of "coal balls". It acted both as tempo- 

 rary preservative and as the source of the calcium and magnesium 

 carbonates which brought about petrifaction. In the fifth section is 

 given an enumeration and comparison of the plants met with in the 

 "coal balls", and "Roof-nodules", respectively, which brings out 

 very clearly the marked difference in the character of the floras 

 represented in these two types of petrifaction. Whilst the "roof- 

 nodules" correspond with a dry land Vegetation which has drifted, 

 the "coal balls" represent a swamp Vegetation that has been fossi- 



