496 E. TATE ON THE LIAS ABOUT RADSTOCK. 



mon associates in the upper portion of the zone — A. obliquecostatus, 

 Ziet., A. Sauzeanus, D'Orb., A. Scipionanus, D'Orb., and Belemnites 

 infundibulum, Phillips. 



The question how much of the Grey Lias should be apportioned to 

 the Buohlandi series seems at first difficult to answer, because of 

 the gradual change in property of the limestones, and their apparently 

 unfossiliferous character. The thick limestone immediately under- 

 lying the Spiriferina bank in the Eadstock section contains Ammo- 

 nites BucMandi and the ordinary fossils of the zone ; it is a constant 

 feature throughout the district. The underlying limestone, about 

 equal in thickness to the other, has yielded Ammonites Johnstoni and 

 A. angulatus at several places, see Medyeat and Tyning sections. 



Section, Medyeat Quarry, 1 mile J¥. from Camerton. 

 Zones ft. in. 



^oj f (e) Thin stone band — 2 



^ £ [(/) Blue clay, no bedding \ to 



[8 



"^ ;§" f (y) Spiriferina-bed 4 



f§ ! \ (h) Blue limestone , 1 1 



^** I Clay parting 3 



8 ^ [ (i) Bluish limestone. Ammonites anyulatus, A. Johnstoni, 



l^-S \ Eucyclns elegans, Macrodon hettangiensis, &c 1 



,2*^ I Six thin limestones. A. Johnstoni, Lima yiyantea, &c 3 2 



It is therefore expedient to regard the upper limestone and its 

 overlying Spiriferina bank as belonging to the BucMandi zone, and 

 the inferior beds of the Lower Lias as one palseontological member, 

 in which, however, Ammonites angulatus and A. Johnstoni, A.pla- 

 norbis and Ostrea liassica have their customary relative positions. 

 Consequently the greater bulk of the Lower Lias limestones in this 

 district belong to the Infra-Lias, as is the case in the Bristol area, 

 where the whole series acquires a very considerable development, and 

 the BucMandi beds are comparatively insignificant, the so-called 

 Lima beds being really part of the A.-angulatus and A.-planorbis 

 zones. 



Though the limestones preserve a pretty general character through- 

 out the Eadstock area, yet a comparison of the following section at 

 Clan Down with that of the Old Pit Quarry, Eadstock, half a mile 

 distant, will show that the series does exhibit sudden changes. 

 Here the Spiriferina bank is still recognizable, and makes a good 

 stratigraphical line ; at Tyning Quarry it is reduced to a minimum, 

 but both the lithological and palaeontological characteristics are pre- 

 served. 



