President's Address. 89 



We are taught by tlie researclies of the various writers 

 quoted the rapid extinction of the Carljoniferous Molluscan 

 fauna after the final deposition of the Upper Limestone 

 Group, its struggle on through the Millstone Grit, its occa- 

 sional appearance in the Coal Measures, and final extinction 

 before the deposition of the Upper Eed Sandstones. 



In a very interesting paper by Mr E. W. Skipsey, " On the 

 Eange and Occurrence of Anthracosia and other shells in the 

 Coal Measures eastward of Glasgow,"* the general range of 

 Anthracosia is said to be from the Ell Coal to the Splint Coal, 

 but still further eastward, on into the Central Lanarkshire 

 Coalfield, as shown by Mr Grossart, several species of the 

 genus extend down to the horizon of the Kiltongue Coal. 



Mr Macconochie obtained a very peculiar variety of A. 

 rohusta (J), at Palacecraig, forming large masses in a calcareous 

 sandstone, 6 feet above the Calderbank Ironstone, which 

 occupies the position of the Kiltongue Coal.-f- Furthermore, 

 a species of Anthracosia has been met with in the Lanark- 

 shire Coalfield as low as the shale above the Lower Drumgray 

 Coal,| whilst in the Douglas district at least three species of 

 Anthracosia are found in a Musselband ironstone not more 

 than 40 or 50 fathoms above the base of the Coal Measures.§ 



Overlying a large number of the coal beds of the Scotch 

 Measures a " Musselband " occurs, which is almost entirely 

 composed of Anthracosim. These beds assume two condi- 

 tions ; they are either composed of compressed shells, often 

 breaking up on exposure, or are solid and coherent, held 

 together by a calcareous cement, 1 1 wdien they become the so- 

 called Coal Measure Marbles, as, for instance, the " Cani- 

 buslang Marble." 



There certainly does appear, following the researcJies of 

 Mr Grossart, a restriction of certain species to certain beds 

 in the Coal Measures, although perhaps not to the extent 

 supposed by some; this is at any rate a question whicli will 

 require further investigation before any strict rules can be 

 laid down. 



* Trans. Geol. Soc, Glasgow, 1866, ii., pt. 2, p. 141. 



t Mem. Geol. Survey, Scotl., No. 31, p. 76 X Ihid., p. 75. 



%lhid., No. 23, p. 90. 



II Grossart, loc. cit. 



