1^22 THE EH^TIC EOCKS OF PYLLE HILL, BRISTOL. 



acters of tlie "Tea-green Marls " are not — as Mr. Woodward 

 seems to imagine — similar to, but, on the other hand, are 

 totally different from those of the Upper Rheetic Shales. 



I come now to the still more difficalt and debatable 

 question. What is the upper boundary of the English 

 Rhastics ? The precise level where the line should be drawn 

 between the Rhgetics and the Lias in the West of England 

 has for some time past been in a state of uncertainty, our 

 leading Rhgetic aathorities, Moore, Wright, Etheridge, 

 Tawney, Boyd Dawkins, and H. B. Woodward, having 

 taken very different views on this point, as will be seen on 

 reference to the literature of the subject.* At the base of 

 the ordinary or typical beds of blue limestone and shale of 

 the Lower Lias, we generally find, in this part of the country, 

 a thin and variable series of cream-coloured or light grey 

 limestones and shales, which are commonly called " White 

 Lias." This quarryman's term is, however, an unfortunate 

 one, for since it was first adopted by William Smith in the 



* Moore, C. — " On the Zones of the Lower Lias and the Avicula 

 Contorta Zone." Quart. Journ. Geol. Soc, vol. xvii. p. 483. 



Wright, T. — '-On the Zone of Avicula Contorta, and the Lower 

 Lias of the South of England." Quart. Journ. Geol. Soc, vol. xvi. 

 p. 374. 



Etheridge, R. — " On the Rhsetic or Avicula Contorta beds at 

 Garden Cliff, Westbury-upon-Severn." Proc. Cottesicold Xat. Field 

 Club, vol. iii. (1865) p. 218. And, " On the Physical Structure and 

 Organic Remains of the Penarth (Rhsetic) Beds of Peiiarth and 

 Lavernock, with a Description of the Westbury-on-Severn Section." 

 Tram. Cardiff' Nat. Soc, vol. iii. (1870-71) p. 39. 



Taivney, E. B. — "On an Excavation at the Bristol Water Works 

 Pumping Station, Clifton." Proc. Bristol Nat. Soc, n.s. vol. ii. 

 (1878) p. 179. 



Dawkins, W. ^.— " On the Rhsetic Beds and White Lias of 

 Western and Central Somerset, etc." Quart. Journ. Geol. Soc, vol. 

 XX. p. 396. 



Woodward, H. ^.— Mem. Geol. Survey. " Geology of East Somer- 

 set and the Bristol Coal-Fields" (1876) p. 69. 



