THE GEOLOGIST. 
DECEMBER, 1858. 
ON THE MARINE SHELLS OE THE SOUTH WALES COAL- 
BASIN. 
By G. P. Bevan, M.D, E.G.S, 
{Read be/ore the British Association, at Leeds, September, 1858.) 
Until of late years, the South "Wales coal-field was considered to be very 
barren in fossils, and those few which were known were all thought to 
be of land or fresh-water origin. During my endeavours to work out 
the geology of this district for the last four years, I have, however, 
discovered sufficient to redeem it from such a reproach, and to prove 
that not only are there fossils, but that these are even in great numbers 
and variety. 
The basin, which occupies portions of Monmouthshire, Glamorgan- 
shire, Breconshire, and Carmarthenshire, may be separated into two great 
divisions, both geologically and chemically. The first is the division 
into upper and lower coal-measures, separated by a thick mass of 
Pennant sandstone, or grit, while the chemical is the division into 
bituminous and anthracitic coals. The upper measures are principally 
found in Glamorgan and Carmarthenshires, the only coal-seam of that 
series in Monmouthshire, being known as the Mynyddswlyn vein. 
Westward of the Taff, however, which is the boundary between the 
two countries, the upper measures appear more frequently, and in 
more regular sequence; while, in Carmarthenshire, we obtain a 
complete section of these beds down to the Pennant rock, in the neigh- 
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