UPPER PORTION OF DUNDRY HILL. 215 



Oolite it was no doubt tlie ironshot-oolitic character which 

 deceived the officers of the Geological Survey, as it has 

 doubtless misled geologists subsequently. However, the 

 fossil evidence is clear, and fairly abundant ; so too are the 

 number of the exposures about the eastern part of the hill. 



2. The Blue Ironshot-heds. 



The hard deposits lying upon the Marlstone, or separating 

 the upper and lower clays where the Marlstone is absent, 

 we have designated by the above name. At times, however, 

 we have colloqaially spoken of them as the " cephalopod-" 

 or " bifrons-beds." 



These strata were exposed by excavations at the western 

 end of the hill and at Maes Knoll ; and at many other places 

 on the flank of the hill the deposits have been found, recognis- 

 able by their peculiar matrix and the contained fossils. At 

 the western end the strata are very thin, but nevertheless 

 give evidence of deposits made during the following hemeree, 

 falcifei-i, hifrontis, striatuli^ dispansi — so that there appears 

 to be wanting any deposit made during the variabilis 

 hemera. 



At Maes Knoll the beds are thicker. There is here dis- 

 tinct evidence of a deposit laid down during the variahilis 

 hemera ; and it would seem that during this time the deposit 

 of the hifrontis hemera was broken up and again redeposited. 

 Such may also have been the case at the western end of the 

 hill. 



The correspondence of this bed or series of beds with 

 those of the Cotteswolds may be seen in our comparative 

 Table III., facing p. 214 ; but we may note that the deposit 

 separating the beds of the falcifevi and striatuli hemerse at 

 Maes Knoll is 18 inches only in thickness, partly, no doubt, 

 owing to the breaking-up of the hifrons-hed and redeposi- 



