THE GEOLOGY OF TYTHEKINGTON AND GHOVESEND. 9 



disclosed by Mr. Hardwicke's quarrying in the oolitic 

 limestone. 



On the further side of the Tytherington tunnel the Palseo- 

 zoic strata are again overlain by Triassic beds, which occupy 

 a denuded depression. I shall speak of these further on. 



Subsection 4. — The oolitic limestones which appear shortly 

 after the line emerges from the Tytherington tunnel are 

 dense strata in which the bedding is inconspicuous. They 

 are being quarried by Mr. Hardwicke. The oolitic structure 

 is very clearly marked, and they closely resemble the Gully 

 Limestone of the Avon section at Clifton. I estimate their 

 thickness at 150 feet. 



They are followed by a series of about 500 feet of bedded 

 limestones, dark in colour, with strong bituminous odour 

 when freshly broken, and largely composed of crinoidal 

 ossicles. They contain, especiall}^ in the lower beds, abun- 

 dant Spiinfers / we also found a gastropod, probably 

 Loxonema. About 75 feet before the 6-mile post is a bed 

 of oolitic limestone. Small quantities of Galena were found 

 near here associated with Barytes. 



These limestones are succeeded, 150 feet from the stone 

 bridge, by the more shaley beds of the Lower Limestone Shales. 

 Beyond the bridge they are somewhat obscured by grass, 

 but Mr. Meredith kindly had them cleared near the line. 

 About 250 feet from the bridge occurs the Bryozoa bed, far 

 less marked than in the Avon section below Cook's Folly, 

 but still readily recognisable — polyzoa {Rlioiyibopora)^ en- 

 crinite ossicles, and other organic remains being converted 

 oxide of iron. 



I confess that it gave me great pleasure to find this bed 

 in the Tytherington section. It has long been known in 

 the Avon section. I subsequently proved its existence at 

 Charlton, near Portbury, at Portishead, and in Woodhill 



