201. 
SILURIAN IN NORTH WALES. 
WwW 
Fig. 1.—Generalized Section from Bala Lake to Pale Hill. 
Bala Lake. Afon Cymmerig. 
E\ 
or AA (ual 
Hirnant. Bwlch Hannerob. 
i 
! 1 
' 1 
1 1 
1 
U ' 
1 
| 
1 2 3 4 5 
1. Rubbly shale. 
2. Bala ash, about 2 feet. 
3. Shales, full of Orthis alternata: containing 
also O. elegantula, O. vespertilio, O. fla- 
bellulum (xare), Leptena sericea, Bey- 
richia complicata, Illenus Davisii, Mo- 
diolopsis sp. Same bed seen again in 
Berwyns near Milltir Gerrig, on Llan- 
gynog road, where we find the upper 
felspathic ash crossing the road above 
thin rubbly shales, and above them a 
brecciated ash, about 20 feet thick, on 
which lie shales in which Orthis alter- 
nata is abundant. In these shales OQ. 
elegantula, Leptena sericea, Beyrichia 
complicata, Nebulipora lens, Favosites 
Jibrosus, Modiolopsis modiolaris, and Cy- 
there wmbonata(?) also occur. 
6 
4. Upper ash-bed. 
5. Fossiliferous shales. 
6. Bala Limestone (for fossils, see description 
of Sect. IT. 6, Gelligrin). 
_7. Massive, comparatively barren shales. 
* 3000 feet above the Bala Limestone (see 
Mem. Geol. Sury. vol. iii. p. 86). 
8. Hard compact grit, 8 feet. 
9. Hard blue shales, 5 feet. | Hirnant beds, 
10. Soft decomposing grits, | consisting of 
9 feet. fossiliferous 
11. Hard blue shales passing} grits and 
above. J 
In Hirnant beds at Bwlch Hannerob, two 
miles north of Aberhirnant, the following 
fossils were found :—Orthis hirnantensis, 
O. sagittifera, O. elegantula, O. testudi- 
naria, O. biforata, Lingula ovata, Ortho- 
nota, Favosites fibrosus, Homalonotus bisul- 
catus, Glyptocrinus basalis. 
Soft blue slaty shales, no fossils, 250- 
300 feet. 
Tarannon shale, 300 feet. 
Hard blue shale, 300 feet; much iron- 
pyrites near top; Graptolites abundant 
in lower part: G. priodon abundant, 
Graptolithus sp. common, Retiolites Geinit- 
ztanus frequent, Orthoceras primevum, 
Orthoceras sp.,Holopella gregaria(?),Rhyn- 
chonella(?). 
15. Grits, with fragments, Enecrinite-stems, and 
other fossils. 
16. Shales. 
14, 15, & 16 are included in what are usually 
known as Denbigh Grits. 
12. 
13. 
14. 
