346 Davies—A Walk over the 
the Deiru joins the valley of the Ceiriog. Now in this glen of the 
Deiru, above the second Ash-bed, there occurs a thin bed of impure 
Limestone, which, though little known, is interesting as being, above 
the Lingula-flags, the first horizon of organic life. We were now 
four miles south of the spot where, in the débris of some old mines, 
it is to be seen; so we looked eagerly, as perchance we might meet 
with indications of its continuance southwards. Nor did we search 
in vain, for here were fragments which, from their position and tex- 
ture, we identified as belonging to it, and in these, as we broke them 
up, we found its characteristic fossils. We were now at the top of 
the hill, and, had the day been clear, we should have seen before us 
one of the most charming valleys of Wales ; but the December fog, 
like a thick curtain, hid it from our view. Blocks of quartz and 
boulders of trap told us we were now crossing the third and highest 
of the Ash-beds, and there, right before us, in the hill Fron Frys, 
rises up the middle and principal band of Bala Limestone, whose 
lowest beds form the slope of the hill we are descending ; we were 
soon vigorously at work, cracking the stones which lie about the 
fields, and with but little regard, I fear, for the rights of property, 
played havoc with the dry stone fences, for here lurk the fossils, 
many nice examples of which soon found their way to our bags: but 
about these we must not gossip now, save to say that we looked 
hard for the Ogygia Buchii ; for I believe, both from the fossils 
associated with it in South Wales, as well as from stratigraphical 
considerations with respect to the Shelve district in Shropshire, 
where it is also found, that this is the horizon where it should be 
sought if it is to be found in North Wales. Our search was in 
vain, though we knocked out plenty of its kindred genus, Asaphus 
(Powisti) ; but concerning Ogygia, so plentiful elsewhere, it must 
still be written ‘not yet found in North Wales,’ as well as ‘ does not 
occur in Ireland.” This is one of the curious examples of the 
apparently arbitrary distribution of species geographically which 
sometimes occur, and which serve to show that the age of any deposit 
is not to be determined solely by the presence or absence of any 
particular fossil. After a half-hour’s rest, with refreshment by the 
fireside of a friendly cottage, we examined the lower beds of the 
Limestone im siév, and then journeyed slowly up the hill. I have 
described the peculiar features of the Bala Limestone elsewhere, 
so here I will only say that the lower beds are massive, they contain 
the usual ferruginous sandy layers, abounding with fossils, and then, 
on ascending to Cefn Coed quarry, their average thickness is 
reduced to five or six inches, and there they are interleaved with 
pale Shales. In these beds occur for the first time the beautiful 
Corals belonging to the genus Heliolites; and some nice examples of 
the Brachiopoda and other families occur, both in the solid Lime- 
stone and also in the Shales. It is interesting to notice how in the 
Shales the fossils are all more or less distorted, while in the Lime- 
stones they retain their original shape; just as if Shales and fossils 
were pressed out—elongated—in one direction, as the layers of 
consolidated Limestone slid down them, when this hill was tilted up 
