RH^TIC BEDS. 25 I 



proved to a depth of 270 feet at Charter House north-east of Cheddar, 

 where a clayey deposit containing Liassic remains in abundance was 

 met with. In the vales west of Frome at Vallis, Nunney, and Holwell, 

 the Carboniferous Limestone is intersected by numerous dykes of 

 mottled clay, white marl and irony sand, with fragments of limes- 

 tone and other rocks. Thin beds of Rhaetic clay, limestone, and 

 conglomerate, may also be observed here and there on the 

 upturned edges of the Carboniferous Limestone. 



In the Limestone quarries at Holwell large bosses of rock have 

 been left untouched by the workmen, and these are portions of 

 dykes or fissures in the rock, filled with extraneous matter. The 

 Limestone is not, however, so largely worked as formerly. On the 

 south side of the road at Holwell, a fissure containing bones and 

 teeth of Rhjetic fishes may be observed. In 1864, Mr. Moore 

 described three cartloads of clay and marl containing Rhcetic 

 fossils which he had obtained from one of the fissures at Holwell. 

 From this material he had procured twenty-nine teeth of the 

 Mammal Microlestes Mooni, together with relics of nine genera 

 of Reptiles, and fifteen genera of Fishes; and he produced 70,000 

 teeth o^ Ac rod us as the result of his labour, stating that the deposit 

 had yielded him probably one million specimens.^ Veins con- 

 taing Rhaetic and Liassic material occur also at Gurney Slade, 

 near Binegar, north of Shepton Mallet. The period of the infilling 

 of these veins cannot be fixed with certainty. Open fissures 

 may, as Mr. Moore suggested, have received material during 

 Rhffitic and Liassic times. On the other hand, fractures in the 

 Carboniferous Limestone may have been produced subsequently, 

 and into the fissures to which they might give rise, material may 

 have been introduced much later.^ 



In Devonshire the Rhsetic beds may be studied between Axmouth 

 and Lyme Regis, at Culverhole Point, Charton and Pinney Bays, 

 as well as at Uplyme, where the White Lias is quarried.^ The 

 White Lias in this neighbourhood contains pebbles of compact 

 limestone, of similar appearance to some layers in the White Lias, 

 and on weathered surfaces these included fragments stand out in 

 relief. The sections east of Axmouth show White Lias, 25 feet ; 

 Black Shales, 20 feet; Grey Marls, 35 feet. (See Fig. 40.) 



The Sun Bed of Temple Cloud, near Glutton, has been recommended for 

 purposes of Hthography, on account of its closeness of texture and general purity. 

 This bed is largely used for road-mending near Radstock. The White Lias beds 

 are used for building-purposes, and are burnt for lime. The black shales are 

 occasionally employed for brick-making. The grey marls have been used for 

 marling land ; they contain alabaster at Watchet and other places. 



The Rhretic beds generally form a gentle escarpment overlooking the vales ot 

 New Red Marl, and the junction with the beds below is frequently conspicuous in 

 the ploughed fields, or in the faces of the more abrupt escarpments, as along the 

 Polden Hills, in Somersetshire. (See Fig. 39.) 



^ G. Mag. 1864, p. 235, Q.J. xxxvii. 67. 



2 C. Moore, Q. J. xxiii. 481, etc. ; J. McMurtrie, Proc. Bath Nat. Hist. Glub, 

 18S3 ; Geol. E. Somerset, etc. (Geol. Survey), p. 173 ; T. R. Jones, Fossil 

 Estherire (Palseontograph. Soc.) 1862, p. 74. 



^ Wright, G. Mag. 1864, p. 290. 



