220 THE KH^TIC ROCKS OF PYLLE HILL, BRISTOL. 



belong to three distinct formations, Keuper, Rhastic, and 

 Lias, are by these authorities included in one of them, viz., 

 the Rheetic. In his excellent Geology of England and 

 Wales,^ my friend, Mr. Horace B. Woodward, defends this 

 course partly on the ground that it had been found most 

 practicable, on the maps of the Geological Survey, to draw 

 the boundary line between the Rheetic and the Keuper at the 

 base of the " Grey Marls," and partly because in certain sec- 

 tions, such as those near Axmouth and Watchet, there are 

 appearances of a transition from the " Grey Marls " into the 

 overlying Avicula co7itorta shales. Following Moore and 

 Wright, I have always myself taken the opposite view on this 

 question. In a paper on the Rhsetics of Nottinghamshire, read 

 before the Geological Society in the year 1882, f I gave ex- 

 pression to that view in the following words : "I cannot admit 

 that the green marls, which in this (Notts) and the adjoining 

 districts come below the Avicula contorta shales, belong to the 

 Rheetic series. For whilst there is always a sharp strati- 

 graphical line of division, with in some cases evidences of 

 erosion, between the ' Tea-green Marls ' and the black 

 ' Paper Shales ' of the Avicula cojiiorta series, there is, on the 

 other hand, every appearance of a gradation between the 

 ' Tea-green Marls ' and the underlying red and green marls 

 of the Upper Keuper formation. Again, whilst there does 

 not appear to be any essential dilf erence in textural character 

 between the green marls which come at the top of the Up- 

 per Keuper and those lower down in that series, there is a 

 very decided textural distinction between the green marls 

 and the overlying Rhtetic shales. The ' Tea-green Marls ' 

 are, like the rest of the Keuper rocks, practically unfossil- 



* 2nd edition, 1887, p. 245, and see also discussion on my paper on 

 the Pylle Hill section, Q. J. G. S., vol. xlvii. p. 545. 

 Quart. Journ, Geo!. Soc, vol. xxxviii. p. 451. 



