OF RHYMNEY AND PEN-Y-LAN, CARDIFF. 481 
beds exposed at the bridge. As this grit, however, is displayed 
more fully in the Rhymney hill at a point just south of the “a” in 
“‘Ty-mawr ” on the map, we had better take our description of it 
from the latter place. 
tihymney Quarry.—On entering the quarry, which is cut from 
W. to KE. in the south side of Rhymney hill, one is struck by the 
massive appearance of its thick-bedded sandstones, which rather 
suggest at first Old Red Sandstone than Silurian rocks. They have 
been well quarried into for use as road-metal, for which they might 
be much more extensively employed, being far better adapted for 
that purpose than the worthless Lias limestone which is largely used 
around Cardiff. 
The exposed surface of the beds rising from some pools in the 
quarry exhibit beautifully regular ripple-markings ; and in some 
places the sandstone is extremely false-bedded. The smooth surface 
of one exposed bed gave a strike of 55° W. of N. with a dip of 33° 
to the N.E. Large joint-planes are numerous, and are always 
coated with red oxide of iron. 
The following is a section of the beds exposed, in ascending 
order :— 
ft. in. 
1. Grey sandstone, with iron-stained fossils (Grammysia cingulata) 
and numerous fragments of mineral charcoal ...................+- 2 0 
(In the lower part of this bed is a thin calcareous band of 
bluish colour, weathering yellowish grey, and containing nume- 
rous badly preserved fossils. ) 
2. Thin parting of grey-blue clay............. Basantobas adobe Sapa dacee se aBacne 
Lo. Massive sandstone, with fucoidal remains, becoming flagey in some 
places, and showing ripple-marks, in others passing into a fine- 
grained conglomerate, greyish and bluish in colour at top and 
bottom, but rusty red in the middle; altogether .................. 23° 6 
31. Welle Sean Faiavs s Gooagnqsanasoeddqndnsnee aos Gnoncenbeeuocobadeua lnpnpeioceaE Ovi 
em Chreyas mau d stone rea: sis oseuiiechs desedamese sve saeqesactiescaasadacsids caries 2 4 
6. Black tenacious clay parting, with light green spots .................. @ 1 
7. Massive sandstone, becoming flaggy in places; light grey to brown 21 5 
8. Compact fine-grained, yellowish, friable sandstone, with dark-grey 
fucoidal impressions, patches of mineral charcoal, and red iron- 
stained casts of fossils, chiefly Lamellibranchs and Univalves ; 
from the prevalence of Ctenodonta subequalis,itmay be termed 
the “ Cienodonta-sandstone” .........sacseceens sree seeescesesecnescns ie 
EME RCV SOME CTINS IAL ES) ree serene ae cle Ne cel sice erileciineisiomjer ening seisle wie sols sctecatisiane I & 
10. Alternating compact and flaggy greyish sandstones ................4. 8 10 
ee Partineaatiblnel shall Oaes.. ese scscecigscseas oveh seas a qeewieatibidsissemesiel 0 2 
12. Alternations of compact and flaggy or laminated greyish sand- 
BHOMECSmMatpeiiesaaseintiatetciienceiiesiclsccie sulci sin stiisinalsiesiantalteclesajsles 8 0 
MUON casabneogeneaconbece nocinr comorgone niches 70 5 
Thus, in the Rhymney quarry, we have something like 70 feet of 
sandstone beds, the lower 40 feet or so being more or less massive 
in the quarry, though when exposed at the surface they weather 
into a great number of thin beds. ‘This massive sandstone or grit 
consists of fine angular particles of colourless quartz, which, though 
very firmly compacted together, yet leave abundant interstices, which 
are more or less filled with brown or red oxide of iron. The sand- 
22 
