THE PRESIDENT'S ADDRESS. 149 



through the counties of Worcester, Stafford, and Cheshire into the 

 Irish Sea, and in a northern line through Warwick, Leicester, Notting- 

 ham, and York to the German Ocean. 



The Trias in England consists of two divisions, the Bunter and 

 Keuper, the middle member so well known on the Continent (the 

 Muschelkalk) has not yet been identified in our country. 



On the western side of the valley the Keuper is exposed, consisting 

 of a, Ked Variegated Marls ; b, Lower Sandstone Marl ; and c, Dolomitic 

 Conglomerate. Several good river sections of the variegated Marls 

 are seen on the banks of the Severn, as at Wainlode Hill, near 

 Tewkesbury, Garden Cliff, near Westbury, and Aust Cliff, near the 

 old passage. The Bunter or New Bed Sandstone does not occur in the 

 valley. 



Between the uppermost beds of the Grey Marls of the Keuper 

 and the lowest beds of the Lias occurs a remarkable assemblage of 

 strata, which have caused a considerable amount of discussion as to 

 the place they ought to occupy among the secondary rocks, and which 

 I long ago described as the Avicula contorta beds, in consequence of that 

 bivalve shell forming one of the leading fossils. Typical sections of 

 these strata are well exposed near Coombe Hill, half-way between 

 Cheltenham and Tewkesbury, in a road cutting leading down to the canal; 

 at Wainlode Cliff, near Apperley ; and still better, at Garden Cliff, 

 near Westbury-on-Severn, where a magnificent exposure of these beds, 

 resting on the Keuper, and overlaid by the Lias, is laid bare by the 

 river. In tbe upper part of the section are dark-grey Shales, inter- 

 sected by bands of Limestone, in which Avicula contorta, Gardium 

 Rhceticum, Axinus, Pecten Valoniensis are gathered. In the lower part is 

 a hard, dark grey siliceous grit, full of bones, spines, scales, and teeth of 

 fishes, belonging to the genera Nemacanthus, Acrodus, Sargodon, 

 Hybodus, Ceratodus, &c. This assemblage of organic debris constituting 

 the bone bed, is claimed by Palaeontologists as the uppermost member 

 of the Trias, seeing that the fish remains all belong to Trias forms. 

 and by others it is considered as the lowest portion of the Lias. I 

 consider the former as the correct determination. The remarkable 

 teeth of Ceratodus, that were found in the bone bed of Aust Cliff, first 

 brought these strata into notice, and the Bristol Bone Bed, as it was 

 long called, became classical ground to the Geologist. It is now ascer- 

 tained that a representative of this genus, once supposed to be extinct, 

 now lives in tbe rivers of Queensland. 



The Lias Formation 

 Occupies the eastern side of the vale, and two-thirds of the western 

 escarpment of the Cotteswold Hills are formed of Lias, which, 

 likewise, is here the basement rock of the Jurassic strata. 



The Oolitic Bocks admit of a division into a Lower, Middle, and 

 Upper series. Each of these groups rests on a great argillaceous 

 formation, upon wbich repose calcareous strata, composed of brown 

 and yellow sands and cream-coloured Oolitic and Pisohtic Lime- 

 stones. The argillaceous strata form wide valleys, which extend 



