474 PKOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



externally, and somewhat resembling the Upper-Lias fish-bed, 

 contains scattered remains of fishes, the Aptychus, and Ammonites 

 semicostatus. 



Ammonites -raricostatus Zone (d, e). — This Ammonite is abundant 

 in a band of nodnlar stone (e) at the top, and by its presence usually 

 distinguishes the line of separation between the Lower and the Middle 

 Lias. 



The Middle Lias (4). — In the Camerton and other sections of the 

 district the passage is at once from the Ammonites -raricostatus zone 

 into thickly bedded Marlstone containing a most abundant and varied 

 series of organic remains. In the section which is at this time being 

 worked at Camerton, the Eoraminif era- clay is the highest member ; 

 but in a continuation of the beds, in a field adjoining, the other strata 

 are present. The Marlstone is here seen to consist of irregular beds 

 about 2 feet thick, immediately under the surface ; but in Old Pit 

 Quarry at Eadstock, at Paulton, and in other sections, it occasionally 

 attains a thickness of 15 feet. The bottom of the Marlstone at 

 Eadstock is conglomeratic, and contains Ammonites raricostatus and 

 other shells, which appear to have been removed from the lower zones. 

 In these marlstones a very prevailing shell is Gryphoea Maccul- 

 lochii ; they also contain abundance of Brachiopoda, amongst which 

 are Terehratula punctata, T. Waterliousii, T. numismalis, Bhyncho- 

 nella ramosa, B. furcillata, &c. "When these were figured from this 

 zone at Eadstock by my friend Mr. Davidson, the distinction between 

 the diiferent horizons in this district was not known ; and these 

 shells were supposed to be from the Lower instead of the Middle 

 Lias. 



Upper Lias and Inferior Oolite (5, 6). — No section of the Upper Lias 

 is uncovered in this district, and, wherever present, it appears to be 

 thin. From the Camerton quarry to the roadway under Tunley the 

 position of the Inferior Oolite is seen. As the latter appears to be 

 the equivalent of the Upper Eagstones of the Cotteswold Hills, there 

 is with these formations a similar thinning out, such as I have 

 intimated in the case of the Lower Lias, and all the beds from 

 the base of the Middle Lias to the higher portion of the Inferior 

 Oolite in the Cotteswolds, are embraced within a thickness of about 

 50 feet. 



I might give many sections showing the same general cha- 

 racters ; but one other, and that not the least remarkable, must 

 suffice. At Paulton there are several quarries in which the White 

 Lias and the Lima-beds above, with the Spirifer-bank and other 

 zones are present, as in the Camerton section. Near Paulton is a 

 roadside quarry in which the Lower Lias is still more feebly repre- 

 sented. 



6. Section in Hunger Road Quarry. 



ft. in. 



Middle Lias. Various beds of rubbly marlstone 6 



( Grrey sandy bed with Leptcena rostrata, Fo- 

 -r T • raminifera, Belemnites clavatus, B. acutus, 

 LowerLias. { ^^ 5i . 



1^ Stone with Ammonites raricostatus 6^ 



