THE RH^TIC ROCKS OF PYLLE HILL, BRISTOL. 223 



year 1815, it has been applied by diiferent authors to very 

 diifereiit things, and in particular to a lower and an upper 

 series of beds, the former of which contain the characteristic 

 E/hastic fossils and are therefore certainly Rhaetic, whilst the 

 latter are, for a similar reason, as certainly Lias. In taking 

 these two distinct series together, their fossils have been 

 commingled, and considerable confusion has in consequence 

 arisen. When I gave my paper on the Rhastics of Notting- 

 hamshire,* at which time I was not aware of this double 

 meaning of the term " White Lias," I was betrayed into 

 using it as equivalent with "Upper Rhgetic"; bat when I 

 came into the Bristol district I very soon found this out, 

 and, in the discussion which followed my paper on the Pylle 

 Hill section, my friend Mr. Win wood entirely misrepresented 

 me when he said, " he was glad to find corroborated Charles 

 Moore's view that the White Lias belonged to the Rhfetic 

 formation." On the contrary, according to my view of the 

 matter, the term " White Lias " is only properly applicable, 

 if it be a legitimate term at all, to those lowest light-coloured 

 limestones and shales of the Lower Lias — the limestones 

 generally predominating — containing such fossils as Modiola 

 miniTYia, Ostrea liassica, and Monotis decussata, which, if 

 present at all, come beneath the regularly stratified blue 

 Lias limestones of the AwiTnonites planorhis series, and rest 

 upon the light grey shales and limestones of the Upper 

 Rhsetic series. The " White Lias," as thus defined, is best 

 developed in, if not limited to, the counties of Somerset, 

 Grloucester, and Dorset. The true White Lias is absent as 

 a distinguishable series from the Liassic districts of the 

 N'orth of England, generally, if not entirely, also from the 

 Midland counties, and apparently also from South Wales. 

 In the immediate neighbourhood of Bristol these beds are 



* loc. cit. 



