292 Mr. Weaver on the Structure the South of Ireland^ 
described at Riversville on the right bank of the Maine a 
low ridge crosses that river and extends some distance be- 
yond it, in which I could discover traces only of the grey- 
wacke formation, and around which the carboniferous lime- 
stone of the vale appears to sweep on the north, east, and 
south, in nearly horizontal position, wherever exposed in 
the adjacent quarries +. For these several reasons my view 
necessarily differs from that taken by Mr. Griffith. 
From the preceding it will be inferred that I do not con- 
sider Mr. Griffiths representations as in any respect invalida- 
ting the conclusions to which I have been led, as exhibited in 
my memoir on the south of Ireland. The day is past when 
it might be authoritatively pronounced that such and such a 
limestone is carboniferous merely because it contains some 
fossils that are common to the latter. 1 have entered at some 
length into this subject in my memoir on the south of Ireland 
and in the Lond. and Edin. Phil. Mag. for August 1 839 , to 
which I beg to refer. But I cannot avoid noticing in this 
place, as a case in point, the communication made by Mr. 
Austen to the British Association, at Birmingham, in August, 
1839 , respecting the fossil remains of the limestones and 
slates of South Devon J, which in its general views so well 
corresponds with the tenor of my publication in the Lond. 
and Edin. Phil. Mag. of the same month, although our re- 
.spective observations and inferences were made independently 
of each other, Mr. Austen conceives that a great identity 
of species can be established between the Radiaria^ Mollusca, 
and Crustacea^ of a portion of the Rhine and those of South 
Devon ; and he states that both districts present many forms 
of animal structure, such as in this country we should call 
carboniferous, and that of forty species which were enume- 
rated, some were hardly, and some not at ail, to be distin- 
guished from those of our mountain or carboniferous limestone. 
Mr. Austen considers as the geological equivalents of the 
slates and limestones of South Devon those of the Rhine and 
Eifel, and that strata in the south of Ireland are of the same 
age ; observing also that many of the same fossils occur at 
Kehou and St. Sauveur in Lower Normandy. He remarks 
also that old. red sandstone is an unfit name to designate the 
limestones and roofing slates of South Devon, or the white 
sandstones of Lower Normandy and Brittany. To which I 
may add, that it is also inapplicable to the older stratified 
rocks of Ireland. 
Memoir on the South of Ireland, § 13. f Ibid., § 51. 
\ See Athenaeum of August 31, 1839, p. CGI. 
