UPPEE POETION OF DUNDRY HILL. 211 



with a species of Haimmatoceras at the base, and species of 

 Di(,7nortieria in its main mass. This is what we called the 

 " Dmnortieria-heds,'* and it is the same deposit as that which 

 we found at the Avestern end of the hill. 



IV. Diagrammatic Section of Dundry Hill. 



The sections of which we have given details above, and 

 other exposures which we noted in our communication to 

 the Geological Society, enable us to construct the diagram- 

 matic section of Dundrj Hill, as shown on the foregoing page. 



Concerning this diagram we would make the following 

 remarks : — 



We have taken the base of the bifrons- and associated 

 beds as a datum level. 



We have found, as the result of numerous trials with the 

 level and many investigations, a thickness for the Dumor- 

 ^{ena-beds of 50 feet at the western end, 55 feet at East 

 Dundry, and 60 feet at Maes Knoll. 



We have found the Marlstone only in the eastern part of 

 the hill, east of the main road, and no signs of it west of the 

 main road. It appears to be a bed which fluctuates con- 

 siderably in thickness ; but perhaps the fluctations shown in 

 the diagram may be partly attributed to the imperfect state 

 of the exposures. We know that it fails altogether at the 

 extreme eastern end of the hill, and also at the western end ; 

 but it must be remembered that the exact point of its 

 westerly disappearance, as shown on our diagram, is only 

 conjectural. 



We find at East Dundry the full sequence of Aalenian 

 deposits, and of Bajocian until the Sauzei hemera — the Iron- 

 shot Oolite. We know that at Maes Knoll the Bathonian, 

 represented by beds of the Garantian^e hemera, rests directly 



