~ 
LOWER PALZOZOIC ROCKS OF ANGLESEY. (5) 
the metamorphic axis, we pass over the Orthis-grit with a north- 
westerly dip, and, west-north-west of Bodsuran, come at once to 
black shales. The green conglomerate has therefore disappeared 
within a mile and a half of Treiorwerth. The shales are here a 
mile and a half broad, forming a syncline whose axis is nearer the 
western than the eastern margin. North of Cwaen-hen, the shale 
contains grit bands, and we appear to have reached its western 
base. About 200 yards to the north, the Clymwr conglomerate 
crops out. 
This section displays a synclinal structure. Taking in the ground 
a little to the north, we find the Clymwr series rising from under 
the western side of the fold; but I am not prepared to affirm that 
the succession is absolutely unbroken. Whether or not the Clymwr 
rock exactly represents the Llanfihangel conglomerate, there is no 
doubt that its position is below the black shales, so that the syn- 
cline is sufficiently complete for our purpose. 
Fig. 5.—Section from Llechyn-farwy to Cwaen-hen. 
(Scale, one inch to one mile.) 
W.N.W. Llechyn- E.S.5. 
Cwaen-hen. farwy. 
i a Maths 
| Cc a 
For explanation see Fig. 4. 
Section (6) from west of Bryn-qwallen to Clymwr (fig. 6).— 
West of Llanerchymedd, the Archean appears in several small 
islands surrounded by conglomerate and grit, which roll about in 
many low undulations. apparently determined by the position of 
underlying masses of the old rock. The black shale also frequently 
Fig. 6.—NSection from west of Bryn-qwallen to Clymur. 
(Scale, one inch to one mile.) 
Clymwr. Ty’n-y-buarth. 
For explanation see Fig. 4. 
appears. The grit series is very thin, for, ina field at Ty’n-y-buarth, 
west of Bryn-gwallen, its basement conglomerate rests upon Archean, 
while in the next field to the west it is conformably overlain by 
shales. A quarry in this field yields Trilobites and other fossils. 
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