Vol. 60.] RH.ETIC OF THE SOUTH-WALES DIRECT LINE. 213 



Sedbury Cliff.— L. Richardson, Quart. Journ. Geul. Soc. vol. lix (1903) 



p. 390 & pi. xxiv. 

 Shepton Mallet. — Vert. Sect. G-eol. Surv. sheet 46, no. 15. 

 Uphill. — Vert, Sect., Geol. Surv. sheet 46, no. 3. 

 Wainlode Cliff. — L. Richardson, Proc. Cottesw. Nat. Field-Club, vol. xiv, 



pt. ii (1903) p. 128. 

 Watch et. — W. Boyd Dawkins, Quart. Journ. Geol. Soc. vol. xx (1864) 



p. 396. 

 Wells. — Vert. Sect., Geol. Surv. sheet 46, no. 14. 



EXPLANATION OF PLATE XVIII. 



Rhffitic Lamellibranchiata. — All the figures are of the natural size. 



Fig. 1. Anomia sp. (See p. 201.) 



Figs. 2 & 2 a. Pecte/i vatoniensis, Defr. (See p. 202.) 



3 & 3 a. Modiola sodburiensis, sp. nov. (See p. 203.) 

 Fig. 4. Cardinia concinna, Sow. aff. regularis, Terq. (See p. 204.) 



5. Fragment of Plicatula cloacina, sp. nov. (See p. 202.) 



[We are greatly indebted to Mr. J. W. Tutcher for the excellent photographs 

 from which the figures in this plate are reproduced.] 



Discussion. 



Mr. Strahan testified to the great value of the observations made 

 by the Authors on the sections that had been opened up on the new 

 line of railway. He had had an opportunity of visiting the 

 Chipping-Sodbury cutting, and had been particularly struck with 

 the form of the Palaeozoic floor under the Rhaetic shales. In one 

 place a small crag, formed by a hard quartz-grit interbedded in the 

 Carboniferous Limestone, projected above the generally-even level 

 of that floor and had yielded great blocks which lay at its foot 

 embedded in the shales. Another projecting mass, formed by the 

 upper beds of the Old Red Sandstone, had formed an island and 

 subsequently a shoal in the earliest Rhaetic sediments. Its surface, 

 recently cleared of the shales, showed the rounding and smoothing 

 by the Rhaetic waves in extraordinary freshness. In strong con- 

 trast to this was the base of the Keuper Marl on the other side of 

 Lilliput Bridge, where the old cliff showed no such wave-action, 

 but had been littered up with a talus of rough blocks. 



The earliest Rhaetic sediments thinned out on the flanks of the 

 Old-Red-Sandstone crag to which he had referred, but the later beds 

 overspread it, curving gently upward and thinning as they did so. 

 The Authors showed the Bone-Red as extending continuously over 

 the surface of the old rock, which suggested that it might be not 

 strictly contemporaneous, but a littoral representative of any part 

 of the Lower Rhaetic shales. It indicated merely a sudden change 

 of physical conditions. 



The Rev. H. H. Winwood referred to the great interest attaching 

 to these Rhaetic beds, at least among West-of-England geologists, 

 and regretted the absence of the Authors, who had done such good 



