Yol. 65.] PLANT-CONTAINING NODULES FROM JAPAN. 203 



Y. Comparison and Contrast with Carboniferous Nodules. 



The Japanese nodules are found in rocks a considerable vertical 

 distance (usually much more than 100 feet) below the coal-seams 

 in their neighbourhood, 1 while the ' coal-balls ' are found in the 

 coal itself and the ' roof-nodules ' in the rocks of the roof imme- 

 diately above the coal, so close as to be sometimes in actual contact 

 with it. Hence, in their geological position, the Japanese nodules 

 differ both from the ' coal-balls' and from the ' roof-nodules.' The 

 difference from the latter, however, is more apparent than 'real, as 

 will be shown later. 



Instead of describing the contrasts in the main features of each 

 of these three types of nodules, a tabulated summary of the principal 

 points is given (p. 202), as the likeness or difference in each case 

 will be more apparent in this form of presentation than in the 

 other. 



YI. Conclusion. 



That the Japanese nodules are not coal-balls is, of course, imme- 

 diately apparent, but that they partake of the nature of coal-balls 

 in having numerous fragments of plant-debris preserved in a mass 

 together, as do the coal-balls, is a point of considerable interest. 

 It is this characteristic which will prove their most valuable one 

 to botanists, for in this they excel all the other plant-petrifactions 

 of Mesozoic age which have hitherto been obtained. It is in this 

 feature, too, that they differ from the Carboniferous ' roof-nodules ' 

 with which they are so closely comparable in other respects. It 

 has been shown (Stopes & Watson, op. cit. p. 204) that the plants 

 in the roof-nodules were presumably waterlogged fragments which 

 had drifted for some time and had been separated from the other 

 debris, the smaller and more delicate of which were scattered (and 

 possibly devoured) and escaped petrifaction. The numerous minute 

 fragments of the Japanese nodules (in which are small rootlets, 

 leaf-scraps, twigs, and spores) could neither have drifted far nor 

 long before they were covered and preserved in that potent pre- 

 servative and petrifying solution, sea-water. 



The presence of ripple-marks and worm-tracks interbedded with 

 the layers, in which also the nodules occurred (see p. 198), is in 

 entire accord with this view, as it proves that the deposits were 

 laid down at no great distance from the shore. Further, the micro- 

 scopic structure of the nodules, with their numerous quartz-grains 

 and crystals, as well as the chemical composition showing 30 per cent. 



1 In one sense they might be considered as lying above some small coals in 

 the second of Dr. Yabe's divisions, namely, the Trigonia- Sandstones. I spent 

 much time in searching for coals in the Mesozoic rocks in actual con- 

 junction -with marine fossils, but found only a few thin coals in the stream 

 Bannosawa, which were clearly in the Trigonia-S&ndstone Series. But, as Yabe 

 says (op. cit. p. 6), the Trigonia-Series is a more littoral deposit than the 

 Ammonite-Beds ; and as there were no fossils immediately above these coals, 

 proof is still lacking that these coals were actually marine. 



