226 THE EH^TIC EOCKS OF PYLLE HILL, BRISTOL. 



the true " White Lias." These beds here, and at other 

 places in the neighbourhood, contain, with other fossils, 

 chiefly casts and therefore indeterminable, Monotis decussata, 

 ModoUa viinima, Ostrea liassica, and Lima gigantea (?). As is 

 the rule with the true White Lias, there is an absence of all 

 reallj characteristic Rhastic forms in these beds, and I class 

 them therefore as Lower Lias. I take the bed " n " of my 

 section, which is evidently the local equivalent of the " Cot- 

 ham Marble," to be the highest distinctive Rhgetic rock in 

 the section. The identity of this bed with the Gotham 

 Marble was questioned in the discussion which followed the 

 reading of my paper to the Geological Society, so I may say 

 now that I subsequently detected the characteristic dendritic 

 markings in this bed at Pylle Hill, and that I have traced 

 this stone to Bedminster Down, two miles further west. 

 Here, in a small excavation in a roadside quarry, just past 

 the last of the houses on the Bridgwater road, this bed may 

 be seen, in a thoroughly characteristic form, resting on the 

 same light grey shales and cream-coloured limestones, with 

 ostracoda, which underlie it at Pylle Hill, and overlain by 

 about four feet of similar rubbly " White Lias " and two or 

 three feet of Amrtionites planorhis beds. In the famous 

 section at Aust Gliff, the position of the Gotham Marble as 

 the topmost bed of the Rhastic is most clearly defined, but it 

 is there directly succeeded by, indeed welded to, Lower Lias 

 limestone of the normal character of beds of the zone of 

 Avimonites planorhis, without the intervention of any true 

 White Lias. The close connection of the Gotham Marble 

 with the Upper Rha^tics and its non-connection with the true 

 White Lias is thus clearly demonstrated, as also is the con- 

 formable sequence of the true White Lias and the Lower Lias. 

 To conclude, then, our description of the Pylle Hill section. 

 The beds underlying the Gotham Marble (beds " i " to " m " 

 of my section), which, with the Gotham Marble (bed " ?2 ") 



