68 



Ammonites Sowerbyi, Miller. Ammonites concavus, Sow., M.G. 



Brocchii, Sow., M.C. subradiatus, Sow., M.C. 



Humphresianus, Sow., M.C. Murchisonse, Sow., M.C. 



Parkinsoni, Sow., M.C. 



and others. 



From this, then, it follows that, while the Gloucestershire 

 Cephalopoda-bed is at the base of the Inferior Oolite or top of the 

 Upper Lias, the Dorset Cephalopoda-bed is near the top of the 

 former ; and yet they have not only been confounded the one with 

 the other, but this position has been supported by the similarity, 

 not the identity, of the Cephalopods, which, indeed, have been held 

 to point to Lias rather than to Oolite. 



Dr. Roll's view of the case seems to be^that, while we have thus 

 the Upper Bagstones, the lower members of the Inferior Oolite are 

 deemed to be absent ; for he says : 



"On the southern side of the Mendips the Inferior Ooolite no- 

 where exceeds 28 or 30 feet in thickness, of which from 8 to 10 feet 

 belong to the lower subdivision. The upper subdivision immedi- 

 ately underlies the Fuller's Earth ; and its light colour, lithological 

 structure, and general poverty in organic remains readily dis- 

 tinguish it from the hard, brown, more or less massive or rubbly 

 limestone beneath, which is everywhere very fossiliferous." 



Now we take it that, although the learned Dr. Holl is right as 

 regards the position of the Dorset Cephalopoda-bed, he is not so in 

 supposing that the lower members of the Inferior Ooolite all thin 

 out in Dorset, our view being that quite 100 feet of the sands, with 

 its occasional bands of shelly oolite, as these occur at Bradford 

 Abbas, really represent the lower oolitic mass of Leckhampton and 

 Crickley in Gloucestershire ; and, in fact, our Dorset sands repre- 

 sent the lower freestones of Gloucestershire. 



At Ham Hill the equivalent of the sand-bed at Babylon Hill is a 

 reddish brown freestone, apparently made up of comminuted shells. 

 At Babylon Hill the brown sandy beds present occasional courses of 

 comminuted shelly oolites. 



The sections here placed in juxtaposition are remarkable for 

 their dissimilarity at first sight ; but if the brown sands were a little 

 more indurated (and the presence of a few more shells or a little 

 more lime might well bring that about) there would not be much 

 difference between the Ham Hill section and several other sections 

 near Sherborne, as well as the one of the Cotteswold Hills. 



