Trish Ordnance Geological Society. 521 
enterprise, but that it will materially tend to elevate Geology, by 
connecting it in a permanent manner with Physical Science. 
“The Rocks of the Scottish Border,” and Mr. W. Stevenson's memoir on 
the Geology of Berwickshire are in the next place treated of ; and the Pre- 
sident then proceeds to notice the 
Irish Ordnance Geological Survey—Tabular List of Irish fos- 
sils.—A compendious volume, entitled ‘A Report on the Geology 
of Londonderry, and parts of Tyrone and Fermanagh,’ has just been 
published by our associate Captain Portlock, R.E., employed in the 
Irish Trigonometrical Survey. Illustrated by a geological map, 
numerous coloured sections, and plates of organic remains, this 
closely packed volume, of nearly 800 pages, is a sample of how 
great a mass of matter may be derived from a small district. Not 
having had sufficient time to study the details of this work, I must 
crave the author's indulgence if I refer only to such parts of it 
as have arrested my attention. Captain Portlock, having some time 
ago discovered a small patch of Silurian rocks in the region of his of- 
ficial labours, commenced a careful and systematic inquiry into the 
nature of the Trilobites with which it seemed to abound, and he 
now presents us with some very valuable results. In a preliminary 
discourse he offers many important remarks upon the affinities and 
anatomy of this group of animals, and after a very elaborate com- 
parison of all the forms which he could detect in his district with 
those published by British and foreign authors, citing among the 
latter several works very little known to us, he arrives at the con- 
clusion, that of sixty species in this palzeozoic tract, fifty-two belong 
to true Silurian strata (for the greater part Lower Silurian), and 
eight only to the enormously developed carboniferous limestone of 
the North of Ireland. This fact is quite in accordance with what 
has long been my belief, that the Silurian or oldest paleozoie group 
is the great centre of Trilobitic life. Describing many new forms, 
which are figured, he establishes several new genera, among which 
the Rhemopleurides, obtained from the Lower Silurian rocks, is a 
very curious and apparently quite distinct trilobite. There are 
but small traces of Upper Silurian or Devonian deposits in this 
district, the greater part of it being covered by a carboniferous 
series, consisting, as the mountain limestone of Ireland is known 
to do, of much sandstone and slate as well as limestone. Find- 
ing in it several shells which are eminently characteristic of the 
lower as well as of the upper beds of that great formation, he in- 
fers, and I think with perfect justice, that the mountain limestone 
of the North of Ireland must be compared with the whole and not 
with the upper part only of that formation in the North of England ; 
an opinion I am prepared to support, by having found last summer 
several shells (notably the Sanguinolaria undata), which are pub- 
lished by Captain Portlock from the north of Ireland, in the very 
bottom beds of the limestone of Berwickshire and Northumberland. 
Confining myself to the researches of this author in the palaozoic 
rocks, on which he has shown so much skill, I must also request my 
hearers to consult this volume of the Irish Geological hs for 
Phil. Mag. 8, 3. No. 148, Suppl. Vol. 22. 2 
