904 T., RUDDY ON THE CAMBRIAN AND 
cross over to the Bala limestone at Rhiwlas, we shall find them 
abundant and of several species. 
Secrron ITI.(fig. 3).—Crossing over the river to a spot a little north 
of the Bala road, in Bodweni Wood, we find a bed which I would 
refer to the Hirnant group. It consists of 15 feet of grit, in which 
I found Orthis biforata abundantly. As far as my experience goes, 
this fossil is much more plentiful in the Hirnant than the under- 
lying beds. Associated with it were a few poor specimens of Orthis 
hirnantensis, O. sagittifera, Arca edmondiiformis, and a species 
which is either Modiolopsis obscura or M. orbicularis. In the wood 
opposite, about a quarter of a mile south of the river, we get on 
to the grits again and find plenty of fossils, consisting of Orthis 
hirnantensis, O. sagittifera, O. biforata, and O. elegantula, with an 
occasional Homalonotus. 
The grits are much disturbed by faults and end abruptly every 
few yards; but they can be traced to Bwlch Hannerob, which I 
have already described (Section I. Nos. 8-10). These grits are the 
same as those coloured Lower Llandovery on the Geol. Survey map; 
but this patch is not alluded to in the Mem. Geol. Surv. vol. ii1. 
Following the line of the grits we lose them under the peat; but 
they again appear on the brow of the hill at the back of Aber- 
hirnant, a little above the road leading up to Maeshir. This is the 
patch alluded to in the Mem. Geol. Surv. vol. iii. p. 85. We find 
here the undoubted Hirnant Limestone in the form of a few con- 
cretionary lumps associated with the usual grits, and both yielding 
fossils plentifully. The commoner fossils found by me here are 
Ortlis hirnantensis, O. sagittifera, O. biforata, O. elegantula, Arca 
edmondiformis, and Modiolopsis pyrus. 
I have no doubt that the Orthis turgida said to occur in the 
Hirnant limestone was only a turgid specimen of O. sagittifera, of 
which I find plenty of distorted and turgid forms. I found here a 
small univalve resembling Holopea exserta of the Rhiwlas limestone. 
In addition to the usual list of Hirnant fossils given n Mem. 
Geol. Sury. vol. iii. p. 86, I have obtained one species of Lingula, 
two of Modiolopsis, or else allied to them, two species of corals and 
one Trilobite ; also a univalve like Holopea. 
A little lower, at the back of Aberhirnant, there is another patch of 
grits and limestones with the usual Hirnant fossils. Here it ends; 
but I have found it again at Craig-Moel-Ddinas, about a mile further 
west, in the Hirnant valley, where I obtained Orthis sagittifera, 
O. hirnantensis, and O. elegantula in a gritty pisolitic mass of rock. 
Half a mile further, at Moel Ddinas, where excavations were recently 
made in search of slates, in the same line of strike I got out of hard 
blue shales fine specimens of Orthis sagittifera of large size, and a 
few specimens of O. hirnantensis. 
