52 THE CARBONIFEROUS LIMESTONE OF SOUTH-WEST GOWER 
bed (19), (15 feet), after which a layer yielding Chonetes ai. 
hardrensis, Spirifer aff. clathratus, Rhynchonella sp., and 
Productus cf. Martini is reached, which appears to be the 
limit of Zj. 
CLEISTOPORA ZONE. 
Sub-zones and K 2 . 
Zone K, which is the last horizon of the Carboniferous 
Limestone, here comprises about 200 feet of red, grey, and 
black flags (20) ; but owing to their being almost devoid 
of fossils, the Sub-zones 1 and 2 cannot be differentiated 
in the South-West Gower series. At one spot only, towards 
the upper part of these flags, a grey limestone was found, 
containing a few specimens of Eumetria cf . carhonaria, and 
Spiriferina octoplicata. Below these limestone flags lies a 
bed of brown shale, from 4-6 feet thick (21), which in turn 
overlies the Old Red Sandstone, represented by a reddish 
Quartz conglomerate (22). The shale bed is presumably 
conformable to the Old Red Sandstone, but as the actual 
exposure here is a very small one and somewhat obscured 
by weathering, this cannot at present be definitely decided. 
The palate bed, so prominent a feature in Sub -zone 
of the Avon Section, does not occur here, nor did I detect 
any teeth in Sub-zone Z 2 , tut as these are not very plenti- 
ful even in the Bristol limestone, a more extended search 
may possibly discover them at Rhosilly. 
The thickness of the four zones described amounts to 
1,500 feet, whilst that of the Syringothyris zone may be 
roughly estimated at nearly 300 feet more. Thus the 
entire thickness of the Carboniferous Limestone in South- 
West Gower must be about 1,800 feet. 
Note. — In Sub-zone Si at Overton a vein of quartz sand con- 
solidated into irregular crusts, exhibits precisely the same appear- 
ance as a recent layer on the surface of the cliffs formed from blown 
sand cemented by carbonate of lime. The vein of Carboniferous 
age is composed of rounded grains and rests on a somewhat irre- 
gular surface of limestone, and is suggestive of a brief period of 
elevation above sea level. A broken shell bed just below the 
sand vein points to a shallow water condition. 
