148 Murchison—Laurentian Rocks. 
that the Bins or Pins of Connemara are, as I had laid it down in 
‘ Siluria,’ simply prolongations of the quartzose and micaceous altered 
Lower Silurian rocks of the Highlands of Scotland.* 
The crystalline green limestone of Connemara is, in fact, encased 
in quartz-rocks ; and, according to my own observation, it has a 
strike from W. by N. to E. by S., or nearly E. and W. But, far 
from being discordant to the direction of the overlying Middle 
Silurian strata with their characteristic fossils, you perceive, as you 
pass from the quartz-rocks with limestone through mica-schists to the 
fossiliferous beds, which are slightly transgressive to those beneath 
them, the whole ascending series has a general strike from E. to W., 
and a decided dip to the north. ‘This is clearly seen as you travel 
from Clifden to the magnificent marine bay of the Killeries. 
As to the presence of an Kozoon in the Lower Silurian rock, I find 
by a letter from Mr. W. A. Sanford, that he entertains doubts as to 
the identity of the Canadian and Irish forms. ‘ Further experiments 
(he adds), which are not yet concluded, lead me to believe that while 
the Canadian form is an immense Nummuline, the Irish one is 
analogous to a Rotaline, very like a gigantic Polytrema. In both 
we have the confluent cells; and, to a certain extent, the structure of 
both is in one part in layers, and in another acervuline. In the 
Trish fossil there is but little if any trace of the beautiful canal- 
system so striking in the Kozoon Canadense, the shell-structure 
being entirely tubular.’ 
It will doubtless be satisfactory to paleontologists if, as Mr. 
Sanford suggests, the Foraminifer of the Lower Silurian of Ireland 
should be found to be dissimilar to that of the Laurentian rock of 
Canada. But I beg to say, that, if the two be found to be identical, 
the green marble of Galway will still remain a true Lower Silurian 
rock, as proved by stratification and the range of similar strata 
from the NW. of Ireland into the Highlands of Scotland. 
The persistence of so low an animal as a Foraminifer through 
vastly long periods is a fact well known to geologists. ‘Thus we 
know that a Globigerina which lived in the Cretaceous age is still 
alive! Nay, even in the Lower Silurian green sand of Russia we 
see silicated remains of Foraminifera indistinguishable from recent 
forms. 
Viewed, therefore, by itself only, the mere presence of Hozoon 
Canadense cannot be taken as a proof that the rock in which it 
occurs is of Laurentian age. Geologists require the further evidence 
of the infraposition of such rock to Cambrian and Silurian strata. 
On this principle, the Canadian rocks were called Laurentian by 
Logan long before an Eozoon was found in them. So also the 
basement-rocks or Fundamental Gneiss of the North-Western High- 
lands will remain of true Laurentian age, albeit no Eozoon may ever 
be found in them. 
* See ‘Siluria,’ last edition, p. 190 (not p. 100, as stated in the last number of 
the GrotogicaL Magazine). 
