THE EH.ETIC EOCKS OF PYLLE HILL, BRISTOL. 225 



the top of the black Paper Shales, I take to be an entirely 

 distinct series of beds from that higher series of light-coloured 

 limestones and shales above defined as the true White Lias, 

 and to belong to a different formation, and I have proposed 

 for them the term " Upper Rhretic," a title which seems 

 distinctly preferable to that of " White Lias " as applied to 

 rocks which differ so markedly from other rocks also termed 

 " White Lias," and which in addition are not Lias at all. 



Many years ago it was pointed out by Edward Forbes that 

 the peculiar dwarfed and limited molluscan fauna of the 

 "White Lias" — meaning by that term rather the Upper 

 Rheetic beds than the true White Lias — indicated that these 

 beds were deposited under exceptional physical conditions, 

 perhaps in inland seas like the Caspian Sea, which had been 

 cut off from the open ocean, and had at first had its waters 

 freshened in consequence.* As evidence in support of this 

 hypothesis it will be interesting •presently to note the 

 character of the organic remains contained in the Upper 

 Rhsetic beds of the Pylle Hill section, which in this as in 

 other respects, may be taken to give the typical characters 

 of these rocks as developed in this part of the country. 



To return to our detailed description of the Pylle Hill 

 section. In that section I take the three or four feet of 

 light-coloured rubbly limestone and laminated shale (beds o, 

 p, q, r of my section) to be the attenuated representative of 



Willsbridge section at Bitton, near Bristol, described by Charles 

 Moore in the Quart. Journ. Geol. Soc, vol. xxiii. p. 498, there were 

 found to be four feet of light blue shales with Estheria viinuta, 

 '-'■ Cythere liassica'''' and Avicula decussata above the Landscape Stone, 

 and which the Ostracoda show must be classed with the Upper 

 Khsetic. 



* Ramsay^ A. C. — " On the Physical Relations of the New Red 

 Marl, Ehgetic Beds and Lower Lias." Quart. Journ. Geol. Soc, vol. 

 xxvii. p. 189. 



