260 Proceedings of the Royal Physical Society. 
outher, the largest of them, Mr Kirkby obtained ZLeaia leydii, Carbonia 
rankiniana, and Spirorbis carbonarius from the roof of one of two thin coals, 
indicating a shehtly brackish-water condition. The evidence afforded by the 
rest of the rocks is scanty, but it seems to denote land and freshwater 
conditions. 
In the Canonbie or Solway region, the Middle Coal Measures contain 
some workable coals which were formerly wrought under the name of the 
“ Byreburn Coals,” and associated with them in the River Esk sections are 
mussel bands made up of the freshwater Carbonicola. No marine bands are 
recorded from these beds, which are not red in colour, though they carry the 
distinctive Middle Coal Measure plants as shown by Dr Kidston. 
Upper Coal Measures.—In the Canonbie region a set of red sandstones, 
fireclays, and a few coal seams have yielded a suite of plant remains which 
have been shown by Dr Kidston to be like those from the Radstock coal-field, 
indicating that they must be classed with the Upper Coal Measures. 
Nowhere in Scotland is the top of the Coal Measures reached. Their 
relation to any Permian rocks is one of violent unconformability indicated by 
the overlap of the Permian and Triassic rocks of the Solway region over the 
denuded edges of all the Carboniferous rocks till they come to rest on the 
Silurian greywackes of the Southern Uplands. 
From evidence obtained during the revision of the Lanarkshire and 
Ayrshire Coal-fields by the Geological Survey, Dr Kidston is at present 
doubtful as to the exact line of division between his Lower and Middle 
Scottish Coal Measures. He finds that some of the Middle Coal Measure 
plants that he relied upon for his classification have been found to occur 
below the line at present adopted, so that part of our Lower Coal Measures 
may be on the same horizon as rocks that are elsewhere classified with the 
Middle Coal Measures. 
(Issued separately, 10th February 1916.) 
