46 PROCEEDINGS COTTESWOLD CLUB 1910 



As the Members of the Cotteswold Field Club may not be 

 familiar with the controversy respecting the question whether 

 these beds should be classed with the Lower Lias above, or the 

 Rhaetic Beds below, perhaps I may be permitted to allude to it 

 shortly. 



The name was introduced by WilHam Smith in 1815, and 

 was then used by the quarrymen, who saw how distinct the 

 colour was from that of the blue beds of the Lower Lias above. 

 In a paper contributed to the Geological Society (Quart. Joum. 

 Geol. Soc, i860, vol. xvi., p. 374), an eminent Member of the 

 Cotteswold Club seems, in a hasty visit to the Beer-Crowcomb 

 Section, near Ilminster, to have mistaken the true position of 

 the White Lias with regard to the zones of the Lower Lias. In 

 describing the Planorbis-Zone, he writes: " In general it con- 

 sists of a series of thin greyish or bluish argillaceous hmestones, 

 with alternating beds of laminated shale ; or sometimes the 

 entire series forms a thick bedded argillaceous cream-coloured 

 limestone called the ' White Lias ' by William Smith." This 

 statement called forth that classical paper of Charles Moore 

 (Quart. Journ. Geol. Soc, vol. xvn., 1861), " On the Zones of the 

 Lower Lias, and the Avicula-contorta-Zone ," in which he 

 clearly showed that a mistake had been made, and that 

 the White Lias had been included in the Planorbis-Zone, 

 whereas it occupied a much lower position. Moore attributed 

 the mistake to the observer not recognising the greyish-white- 

 looking bands of stone in the blue Lias quarry from the creamy 

 hmestones occupying a much lower position. Since then, the 

 true position of the White Lias, as belonging to the top of the 

 Rhaetic Series, has been, with one or two exceptions, generally 

 recognised. 



With these few preliminary remarks I will proceed at once 

 to describe the section. 



The total thickness of the White-Lias beds (using this 

 term in a broad sense, but to be more correct, Upper- 

 Rhietic beds) was about 16 feet 4 inches, measuring, that 

 is, from the lowest exposure of an ii-inch bed of White 

 Lias up to the clay on the top of the " Sun- Bed " of 

 William Smith. The fossils were by no means plentiful, 

 but the usual casts of bivalves (Modiola, etc.), occurred in the 



