THE CARBONIFEROUS LIMESTONE OF SOUTH-WEST GOWER 51 
At the north-east angle of Rhosilly Bay and immediately 
below the village, the Carboniferous Limestone rises sharply 
up over the Old Red Sandstone ; but the junction of the 
two is hidden by an enormous mass of detritus. 
Sub -zone 
The flags just referred to are seen here to overlie about 
10 feet of unfossiliferous dark shale (16), under which a 
blue limestone is reached, packed with broken crinoid 
stems (17) ; a few fragments of calices were procured but 
too broken up to permit their being identifled. In this 
bed Bryozoa are somewhat common, Glauconome sp. being 
the chief form. The only coral met with was Zaphrentis 
aff. Phillipsi (rare). Under this layer was a stratum of 
20 feet (18), very rich in Orihotetes crenistria, Productus 
cf. Martini, Spirifer aff. claihratua, Leptaena analoga, 
Chonetes cf. hardrensis, which typify Sub-zone Z^. Cho- 
netes cf . hardrensis is the characteristic fossil of this bed, and 
in places the limestone seems almost entirely built up of it. 
Gastropods occur at this horizon in a bed only a few 
inches thick, but they are not comparable in variety nor 
in abundance with those found in the bed of Sub-zone S^. 
The chief genera are Bellerophon and Naticopsis, and 
with these is associated an elongated slender Orthoceras. 
These beds are the last which can be traced in the 
Rhosilly section, the underlying beds, however, are to be 
found on the banks of a little stream entering the sea at 
Parkmill,^ on the east side of the Gower Peninsula. Though 
somewhat obscured by sandhills, the highly fossiliferous 
Chonetes bed, so noticeable a feature at Rhosilly, can be 
easily made out. About 14 feet of dense unfossiliferous 
limestone (19) divide it from a thin seam (19), with 
numerous but badly preserved specimens of Spirifer aff. 
clathratus. No trace of any organism occurs in the next 
1 Vide Section D on page 45. 
