Baily— Cambrian Rocks and Fossils. 387 
mud. What he supposed to be the fragment of a Trilobite, or allied 
Crustacean, and described under the name of Paleopyge, appears to 
want that definition of character which would entitle it to be con- 
sidered as of organic origin: we still have, however, in these the’ 
most ancient of the fossiliferous rocks, good evidence of the existence 
of organic life, and that not of the lowest type. 
In Ireland, rocks referred to the same series as those of North 
Wales occur immediately opposite Anglesea and Caernarvon, at the 
Hill of Howth near Dublin, Bray Head and other places in the 
northern part of the county of Wicklow, as well as a large district 
which includes the Forth Mountain in South Wexford. These rocks 
consist of a great series of sandstones or gritstones and slates, often 
interstratified with large masses and veins of quartz-rock.* 
At the promontory of Howth, in the county of Dublin, the Cam- 
brian rocks extend over a small area of only about two miles, consist- 
ing of large masses of quartz-rock, interstratified with green grits 
and green and purple slates; the beds being often highly inclined, 
contorted, and so confused that it is impossible to make out any con- 
tinuous section.t Only very faint traces of organic life have been 
met with at this place; and for these we are indebted to the perse- 
verance and untiring zeal of the late Dr. J. R. Kinahan, a young 
naturalist of great promise, whose loss has been severely felt amongst 
scientific men in Ireland. ‘The specimens he discovered and pre- 
sented to the Geological Survey are included amongst their collection 
of fossils in the Museum of Irish Industry, Dublin, and afford (al- 
though few in number) tolerably good evidence of the occurrence of 
that remarkably characteristic fossil of the Irish Cambrians, the 
Oldhamia, so abundant at Bray Head, in the county of Wicklow, 
and hereafter alluded to. ‘These specimens, and another since col- 
lected by Mr. C. Galvan, of the Geological Survey, appear to be 
correctly referred to O. antiqua: the impressions are, however, 
somewhat indistinct and sparingly distributed. The beds from which 
they were obtained are situated on the north shore, at what is called 
Puck’s Rocks, and are composed of a yellowish slate, readily split- 
ting into fine laminz, very similar to the brown laminated schists 
of Carrick Mountain, in the county of Wicklow (hereafter alluded 
to), which are often covered by impressions of the same species of 
Oldhamia in much better preservation. 
From beds immediately overlying those containing the Oldhamia, 
Dr. Kinahan also procured slabs with tortuous markings like tracks. 
On consulting the maps of the Geological Survey of Ireland,t it 
will be seen that the Cambrian district of North Wicklow commences 
about two miles north of the town of Bray, extending southwards to 
* For a description of the geology of this district, see a memoir by Messrs. Jukes 
and Haughton, ‘On the Lower Paleozoic Rocks of the South-east of Ireland,’ 
Trans. Royal Irish Academy, vol. xxiii. p. 563, &c. (1859). 
{~ Vide sheets 112 of the one-inch scale, Maps of the Geological Survey of Ire- 
land, and Explanations to sheets 102 and 112 (1861). 
¢ Sheets 121 and 130. 
cic 2 
