UPPER PORTION OF DUNDRY HILL. '227 



boundary-line of Inferior Oolite coincides with onr own 

 (beg'inning of deposition in Aalenian age), and is drawn at 

 the top of the Bumortierice clays, along by the village and 

 by " the Grove," until about 250 yards north of Castle 

 Farm, when it strikes off to the top of the " Cephalopod-" 

 or " hifrons -beds'' ; and at Castle Farm it is about 150 yards 

 outside our line. It continues on or a little below this 

 horizon round the southern flank of the hill to Rackledown 

 Farm, when it drops below the Marlstone — as much below, 

 in fact, as it ought to be if the Marlstone were really the 

 Ironshot Oolite of the Sauzei hemera. It continues at this 

 level round both sides of the East Dundry Yale, with the 

 result that the Survey's base-line of Inferior Oolite is, at 

 the head of the valley, as much as 650 yards outside 

 ours. 



Their boundary-line then continues to run on this infra- 

 Marlstone level to Maes Knoll, where in drawing our line 

 we differ from the Survey to the extent of about 100 feet 

 in vertical thickness, and in some places, as at the north- 

 eastern corner, to the extent of about 250 yards in hori- 

 zontal distance. 



From Maes Knoll their boundary- line continues along the 

 northern flank of the hill on the infra-Marlstone level until 

 it approaches the main road whence we started, when they 

 show a lengthy northward prolongation of "Inferior Oolite" 

 by the eastern side of the bend in the main road. This 

 projection is not only some 400 yards outside the boundary 

 of what they call Inferior Oolite on the other side of the 

 road, but it is even some 250 yards outside what we take 

 to be the horizon of the Marlstone. 



It will thus be seen that, except along the northern flank 

 of Dundry Hill, to the west of the main road, the Survey 

 have mapped far too great an area as Inferior Oolite, and 



