DENBIGHSHIRE GRITS, NEAR CORWEN, NORTH WALES. 495 



made their first appearance. Again, the habitat of Nematojohycus, 

 if it at all resembled the present Lessonice in growth at the bottom 

 of the ocean, may have survived many changes between land and 

 sea during the deposition of the Upper Silurian rocks, while yet the 

 sea-bottom or bed of the Silurian Sea was never exposed or became 

 dry land. The finding and determining the nature of these remains 

 opens up a great problem, so far as the age, continuity, and distribu- 

 tion of Cryptogamic life in palaeozoic time is concerned. 



EXPLANATION OF PLATE XXV. 



Fig. 1. Nematophycus Hicksii : cross section, x 200. 



2. Ditto : longitudinal section, X 200. 



3. Ditto : tubes filled apparently with granular substance, X 325. 



4. Ditto : tubes covered by fine transverse lines, X 325. 



5. Ditto : portion of stem, natural size. 



6. Ditto : fragments, ditto. 



7. Pachytheca : x 6. 



8. Ditto : portion of wall, X 200. 



9. Ditto : fibre in wail, X 200. 



10. Microspores, probably of a Lycopodiaceous plant, X 15. 



Discussion. 



Mr. Carruthers spoke of the importance of Dr. Hicks's discovery, 

 and said that after the President's note it was needless for him to 

 add much. He had come in the main to the same conclusion. The 

 view of the significance of the Pacliythecce was interesting : but the 

 data which had come before himself hardly warranted his regarding 

 them as Algae. He explained the reasons why he was unable to 

 accept the President's view, and agreed with that of Sir Joseph 

 Hooker — namely, regarding them as Lycopodiaceous. He thought 

 also that the signs of a vascular axis in some of the specimens 

 proved a land-flora ; also there were some spores, not sporangia, 

 which bore out this view. 



Mr. Hopkinson said that the Graptolites were partly Middle 

 Silurian and partly Upper Silurian forms, some being Llandovery 

 species, here dying out, and others Wenlock species, first appearing 

 here. The change in type seemed to imply an alteration in physical 

 conditions. 



Mr. De Ranch referred to some Ludlow pebbles at the base of the 

 Carboniferous, and said that anthracite occurred in beds of the Lake- 

 district of about the same age. 



Prof. Duncan spoke of the good fortune which had attended Dr. 

 Hicks's investigations in unpromising ground. The cellular plant 

 discovered by him was a very remarkable one ; it reminded him of 

 Codium. The undulated underpart of the cellulur structure was 

 very remarkable, indicating a general rugosity or a spiral fibre ; that 

 fibre occurred in modern water-plants. In one part there was 

 something like a dissepiment. As in the beds above the Gannister, 

 there might be a common link here of land- and water-plants. He 



