240 
THE GEOLOGIST. 
tance of thirty-two miles^ the breadth of the district being seldom 
more than three miles, and the greatest elevation 863 feet. The 
strata consist of a reddish-brown sandstone, covered unconform- 
ably by carboniferous rocks, and alternating with shale, and con- 
glomerate which is occasionally trappean. North of Ballagh- 
deneen, County Mayo, there is a considerable tract of metamor- 
phic conglomerate, passing sometimes into semi-porphyry, and 
at other locahties becoming schistose, and passing into compact 
brown shale. In the midst of the metamorphic porphjrry at 
Egool, immediately to the south of the Mountain of MuUa- 
ghanoe, is a series of rocks composed of alternations of brownish 
red sandstone and shale, greenish grey quartzite and slate, and 
impure limestone. Out of nineteen species from this limestone 
which occur in England, three belong to the Caradoc sandstone, 
three are common to the Caradoc and Wenlock formations, and 
sixteen to the Wenlock and Upper Silurian. Another district 
of the red sandstone and conglomerate is situated to the north of 
Castlebar, and occupies the same geological position in regard to 
the carboniferous series, as those already mentioned, but as yet 
no fossiliferous beds have been discovered within its limits. At 
Kildare the author had discovered thirty-two species of fossils in 
a mass of limestone : of these, eighteen are described in Mr. 
Murchison^s Silurian system, all of which occm' in the Caradoc 
sandstone, five of them, however, being common to the Wenlock 
and upper rocks. 
On the Important Additions recently made to the Fossil Contents 
of the Tertiary Basin of the Middle Rhine, by R. I. Murchison, 
Esq. 
After a sketch of the geographical limits and geological rela- 
tions of the tertiary deposits which occupy the Valley of the 
Rhine and Mayne, around the tovras of Mayence, Frankfort, and 
Darmstadt, Mr. Murchison gave an account of the recent disco- 
veries made by M. H. von Meyer, M. Kaup, of Darmstadt, and 
M. Bronn, of Heidelberg. Of the animals of this tertiary basin 
