466 British Association — J. Home, F.R.8., etc. — 



HoloptycMus. Dr. Traquair has also recognized in Dr. Flett's collection 

 fragments of Asterolepis, a genus characteristic of the Upper Old Eed 

 Sandstone, and which, as proved by Dr. Flett, occurs in the ' Thurso beds ' 

 of the Orkneys. The interest attaching to this discovery is very great, for 

 Dr. Flett contends that it indicates a fourth life-zone in the Orcadian 

 series, and, further, that it tends to span the break between the Orcadian 

 division and Upper Old Red Sandstone. 



In the Upper Old Red Sandstone on the south side of the Moray Firth, 

 Dr. Traquair recognized two life-zones, and subsequently, with the assist- 

 ance of Mr. Taylor, Lhanbryde, a third ; in the following order. The 

 lowest is that of the Nairn sandstones with Asterolepis maxima (Ag.) ; the 

 second, that of Alves and Scaat Craig with Bothriolepis major (Ag.), 

 Psammosteus Taylori (Traq.) ; and the highest, that of Rosebrae, the fauna 

 of which, according to Dr. Traquair, has a striking resemblance to the 

 assemblage in the Dura Den Sandstones in Fife. 



Before 1876 all the Carboniferous areas in the great midland valley of 

 Scotland had been mapped by the Geological Survey. The extent and 

 structural relations of the various coalfields were determined according to 

 the information then available, and shown in the published maps. But 

 the rapid development of certain fields in the east of Scotland necessitated 

 a revision of them, which has lately been done. The Fife Coalfield has 

 been re-examined by Sir A. Geikie, Mr. Peach, and Mr. Wilson, and the 

 oil-shale fields in the Lothians have been mapped by Mr. Cadell. An 

 important memoir by Sir A. Geikie on " The Geology of Central and 

 Western Fife and Kinross" has just been issued by the Geological Survey, 

 in which the structure of these coalfields is described. Mr. Cadell lately 

 gave an account of the geological structure of the oil-shale fields in his 

 presidential address to the Edinburgh Geological Society. 



Within the period under review detailed researches of great importance 

 on the fossil flora of British Carboniferous rocks have been carried out by 

 Mr. Kidston, to which reference ought to be made. The results are of the 

 highest value for correlating the strata in different areas.^ By means of 

 the plants he arranges the Carboniferous rocks of Scotland in two great 

 divisions : a lower, comprising the Calciferous Sandstone and Carboniferous 

 Limestone series ; and an upper, including the Millstone Grit and the 

 Coal-measures, there being a marked pal^ontological break at the base of 

 the Millstone Grit. He shows that the upper and lower divisions of the 

 system, not only in Scotland but in Britain, are characterized by a different 

 series of plants, not one species passing from the lower division, save in 

 the case of Stigmaria, into the upper. From his researches it appears 

 that, among ferns, Neuropteris is all but unknown in the lower division, 

 whereas in the upper it is very abundant. The Sphenopterids are pro- 

 portionately common in both divisions ; but those of the lower are usually 

 characterized by cuneate segments, while those of the upper have generally 

 rounded pinnules. Alethopteris, so common throughout the whole of the 

 upper series, is entirely absent from the lower. The genus Catamites, 

 which is extremely plentiful in the upper, is almost entirely absent from 

 the lower division, where its place is taken by Aster ocalamites. The 

 Cordaitece are also rare below the Millstone Grit, though very plentiful 

 above that horizon. Sigillaria, so rare in the Lower Carboniferous rocks, 

 is extremely abundant in the upper division, and particularly in the middle 

 Coal-measures. In short, Mr. Kidston concludes that the floras of the two 

 main divisions of the Carboniferous system, though belonging to the same 

 types, are absolutely distinct in species and in the relative importance of 

 the genera. 



^ " On the various Divisions of British Carhoniferous Eocks as determined by 

 their Fossil Flora " : Proc. Eoy. Phys. Soc. Edinb., vol. xii (1893), p. 183. 



