MORRIS — BRITISH FOSSILS. 
139 
UrPEU SlT-UIllAN. 
(Thickness, 5,000 feet.) 
Tilestone and Ludlow beds. 
Wenlock and Woolhopc beds. 
Middle Silurian. Lo-wer Silurian. 
(Thickness, 2,000 feet.) (Thickness, 19,000 feet.) 
Caradoc and Bala. 
Upper and lower 
Llandovery rocks. 
Llandoilo flags. 
Lingula beds. 
LoNGMYND or BOTTOM RocKs, or Lower Cambrian of Sedgwick. (Thickness, 
26,000 feet.) 
A. Lower Cambrian (Sedgwick). 
Lower Cambrian, Sedgwick, Lyell ; Cambrian, Longraynd, or Bottom i-ocks, 
'urchison, and the Geological Survey ; Cambrian, in part, Fhil/ij>s ; Tremadocian, 
Murchison, ^ „ , 
in part, Woodioard ; Huronian, Logan 
Harlech grits, Bangor & 
Llanberris slates, 
Longmynd schists, 
St. David's schists ; , 
in Wales. J 
Skiddaw slates 
and grit-stones, 
Cumbria. 
(Lower Cumbrian 
of Sedgwick.) 
Ross-shire con- 
glomerates, 
Scotland. 
Grits and slates 
of Wicklow and 
Wexford, Ire- 
land. 
The lower Cambrian rocks of Wales consist of grits and conglo- 
merates, at Harlech, and of alternations of gritstones and slates at 
Bangor and Llanberris ; the latter place affording the best roofing- 
slates. The probable equivalents of these rocks in Anglesea are con- 
torted and crystalline schists, of gneissose, micaceous, and chloritic 
characters. The Longraynd and Haughmond hills of Shropshire 
consist of a thick series of dark purple and greenish schists, grits, and 
sandstones, estimated at 26,000 feet in thickness. These flagstones 
exhibit trails and holes of worm-like animals, also ripple-marks, and 
other evidences of littoral or shallow- water conditions. They also yield 
relics of a trilobite. Similar rocks, but apparently without fossils, 
occur near St. David's, in South "Wales. 
To this division Professor Sedgwick refers the Skiddaw slates and 
grits of Cumberland ; these are of great thickness. The purple and 
green grits and slaty rocks, with occasional interstratified quartz, of 
Bray Head, Wicklow, and the adjacent coast, in Ireland, belong to this 
group. In their upper portion have been detected numerous worm-like 
markings, and the curious fossil known as Oldhamia. 
The great red conglomerates and sandstone of the north-west of 
Sutherland and Ross, in Scotland, have lately been proved to be of this 
lower Cambrian age. 
The fossils of these rocks are very few, comprising doubtful remains 
of fucoids, traces of sea-worms, and a branched zoophytic form, pro- 
visionally referred to the Bryozoa. 
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