204 THE GEOLOGICAL STRUCTUEE OF THE 



posited during the Murchisonse hemera, and part of it, per- 

 haps, during the bradfordensis hemera ; but we have no 

 evidence on the latter head. 



The horizon of Sonninia jissilohata-ovalis (bed 10), which 

 is well marked, may be noted as a very good datum-line 

 from which to commence the correlation of the strata in the 

 upper portion of this section with those of the western end of 

 the hill. But the most noticeable beds are those which yield 

 a fine series of Witchellise^ and the overlying Ironshot Oolite, 

 yielding Sonninise of the propinquans-type, with " Stepliano- 

 ceras " Sauzei. These beds are wanting from the western 

 portion of the hill ; but in this part they have escaped 

 " The Bajocian denudation." ^ Still, there is a non-sequence 

 between beds 5 and 4, and this gap is not filled by any 

 strata shown in any of the sections at Dundry. In order to 

 make the sequence complete, strata laid down during the 

 niortensis-Humphriesiani hemerse should be present.^ 



An interesting fact, and one of economic importance, con- 

 cerning this section is the great attenuation, together with 

 change in character, of the deposit contemporaneous with 

 the freestone of the quarry near the church. In the middle 

 of the hill the freestone deposit is only represented by 

 thin-bedded limestones about 4 feet in thickness. 



It is necessary now to pass to the eastern end of the hill. 



1 See p. 219. 



2 See S. S. Buckman, ' The Bajocian of the Sherborne District,' 

 Quart. Journ. Geol. Soc, vol. xlix. (1893), p. 500, section of Frogden 

 Quarry. 



