84 PROCEEDINGS COTTESWOLD CLUB 1910 



In the deposit of bradfordensis hemera exposed on the 

 flanks of the Minchinhampton-Common and Rodborough-Hill 

 upland, specimens of Nerincea are not uncommon, and on the 

 evidence of other sections would appear to occur at about the 

 same horizon as Rhynchonclla Tatei, although where the one is 

 common, the other is not, and vice versa. 



It may be that at the northern end of the South Cottes- 

 wolds only the top-portion of the Oolite Marl is present. Certain 

 sections in the Mid and North Cotteswolds have suggested 

 either a slight break between the deposits of Murchisonce and 

 Bradfordensis hemerae, or very little deposit being made locally 

 in early bradfordensis times. But be this as it may, towards 

 the close of bradfordensis hemera there was considerable crust- 

 flexuring and production of slight anticlines and synclines. It 

 is improbable that any important deposit was made over the site 

 of the present South Cotteswolds during the concavi hemera. 

 If it was, then there is no trace of it left now. The eleva- 

 tion which took place in late bradfordensis hemera and the 

 erosion which ensued, have been termed the " Aalenian 

 Upheaval" and "Denudation." Probably the anticlinal and 

 synclinal axes were not widely divergent from those which 

 were developed at the close of the time-of-formation of the 

 Bajocian deposits. 



Upon the disturbed Aalenian rocks the Bajocian deposits 

 were laid down — the successive beds overlapping one another 

 as subsidence proceeded. In the South Cotteswolds, and then 

 only at the northern end on Rodborougli Hill, the Lower 

 Trigonia-Gni immediately succeeds the Upper Freestone, and 

 it is in turn followed by the Buckmani-Gvit, which does 

 not extend across the Nailsworth Valley on to Selsley Hill. 



(xiv.) Lower Trigonia-Grit [discike). — This is of the usual 

 lithic aspect — a grey-brown shelly ragstone with iron-specks, 

 and contains the ordinary assemblage of fossils. From it, at 

 Rodborough Hill, many new species were obtained by Lycett. 



(xiii.) Buckmani-Gnt {post-discitcB). — The Buckmani-Gxii, 

 which has about the same geographical extent as the Lower 

 Trigonia-Gni in the South Cotteswolds, is definitely identifiable 

 on account of its having yielded at Rodborough Hill specimens 

 of Terebratula Buckmani and Tcr. crickleyensis, and separable, 

 as regards lithic structure in the relative absence of iron-specks, 

 and by its more arenaceous character. 



