TRANSACTIONS OF SECTION GC. 477 
although in places, especially near the top, it is regularly bedded. Grains 
rounded. 0 to 150 feet. 
7. New Faunal Horizons in the Bristol Coal-field. 
By Hersert Bouton, F.R.S.E., F.G.S. 
The well-known rarity of animal remains in the Bristol coal-field is 
proving to be due rather to the concealment of the measures beneath newer 
rocks than to any actual absence of fossils. 
In 1906-7 the writer determined the existence of four horizons each 
possessing a marine fauna, between the top of the Millstone Grit and the 
lowest workable seam in the Ashton district ; and further work upon the 
beds lying above the Bedminster seam at South Liberty Colliery, Bedminster, 
and at Coalpit Heath in the north of the basin, has proved the occurrence 
of others. 
A section at South Liberty Colliery is as follows :— 
Feet. 
Strata ... are ear thy 5c so Bos ee 127-4 
Black Shale with Anthracomya ... Bic so: ae 4:11 
Strata ... aaa As faz ar ae ALE te 337°8 
Grey Shale with Anthracomya ... oes she ae 3-7 
Strata ... dae 265 ae aie me nae as 2:0 
Dark grey Shale with shells “ae ie “ae sae 28 
Strata ... ane Aine Si =oe ore nee Hie 150:0 
Black shell-bearing Shale ... ps as neo re "3°6 
Strata ... des one mee Sit wi. oes od 134-4 
Bedminster Seam .., nO. foc aoe Sct ate 30 
At Coalpit Heath, a black shale forming the roof of the High Vein 
(Hollybush Vein of Parkfield) has proved exceptionally rich in specimens 
of Leaia Leidyi var. Salteriana, whilst Estheria cf. tenella, and Anthra- 
comya Phillipsi also occur. 
8. Description of the Avon Section, Bristol, in illustration of Dr. A. 
Vaughan’s Work on the English Carboniferous Limestone. By 
Professor S. H. Reynoups, M.A. 
9, Lithology of the Carboniferous Limestone of Burrington Coombe, 
Somerset. By Professor 8. H. Reynoups, M.A. 
10. Unconformities on Limestone and their Contemporaneous Pipes 
and Swallow-holes. By E. EB. L. Dixon, B.Sc., F.G.S. 
Caleareous rocks differ from other commonly occurring types in being 
appreciably soluble in atmospheric waters, and, in consequence, being eroded 
along underground channels where situated above saturation-level. Thus 
it is that one of their most striking physiographic characteristics is the 
occurrence in them of numerous caves and swallow-holes, of all sizes and 
shapes, often containing either debris of overlying rocks or deposits formed 
in them in situ. It is the purpose of this note to draw attention to the 
way in which this characteristic is reflected in the nature of certain uncon- 
formable junctions of limestones with younger rocks. 
Unconformities may be divided, for our purpose, into two groups. In 
the first the underlying rocks have an approximately plane upper surface, 
the plane of the unconformity, and have evidently been base-levelled, by 
