SILURIAN IN NORTH WALES. 205 
Fig. 3.—Section in Bodweni Wood, North of the Dee. 
1. Soft blue slaty shales which usually underlie the Tarannon shale. 
2. Hard compact grit, 15 feet. 2c. Band of soft decomposing grit, 9 inches 
thick. he fossils found a short way into the hard grit (compare Sect. I., 
bed no. 10). Orthis_biforata (plentiful), O. hirnantensis, O. sagittifera 
(scarce), Palearca (Modiolopsis) sp., either obscura or orbicularis, Arca 
edmondiiformis, Favosites (Stenopora) fibrosus, an Encrinite. 
3. Shales (=bed no. 7 of Sect. I.). 
Srction IV. (fig. 4).—The Hirnant beds again appear in a small 
quarry on the side of the hill west of Cwm-yr-Aethnen, where there 
is a fossiliferous pisolitic dark-coloured limestone, No. 3. Under the 
limestone there is 20 feet of highly fossiliferous shales, in which I 
got two small specimens of Nebulipora lens in addition to the usual 
Hirnant species. Above the limestone is a band of rubbly shales 
with concretionary limestones, No. 4, and above that a band of soft 
decomposing grit, No. 5, with shales above it, all of them being 
fossiliferous. 
A little further west, on the brow of the hill, another patch appears 
containing the usual fossils, and here it is altogether lost (see Mem. 
Geol. Surv. vol. iii.). 
Fig. 4.—Section near Cwm-yr-Aethnen. 
. Shales (=no. 7 of Sect. I.). 
. Highly fossiliferous shales, full of Hirnant species, 20 feet. Orthis hirnan- 
tensis, O. sagittifera, O. biforata, O. elegantula, Nebulipora lens, Favosites 
(Stenopora) fibrosus, Encrinites. 
. Band of pisolitic limestone, 2 feet (fossils). 
Shale aud concretionary limestone, 3 feet (fossils). 
. Band of soft decomposing grit, 2 feet (fossils). 
. Fossiliferous shales passing up into slaty shales. 
. Soft blue slaty shale underlying the Tarannon shale. 
Sucrron V. (fig. 5).—Believing that the Hirnant and Lower Llando- 
yery Grits would turn out to be identical, I went across to Cefn-bwlan, 
at the head of the Llanwddyn valley, where the Lower Llandovery 
Grits are said first to appear (see Mem. Geol. Sury. vol. ii. p. 206). 
Here I found the usual Tarannon shales (No. 3) cropping out of the 
bed of the brook; under that a bed of fine blue shales (No. 2); and 
under these, cropping out of the peat, we have hard compact grits 
with interbedded shales (No. 1). It is but a small patch rising out 
of the peat. These Lower Llandovery Grits occupy the same strati- 
Dor 
~ID OU oo 
