Harkness on Metamorphic Rocks, §c. of Connemara. 471 
they can wander at pleasure far away from water, and even defy 
the powerful heat of a tropical sun. Perhaps no stratum affords 
greater abundance of long-tailed forms (Lobsters) than the Litho- 
graphic Limestone of Solenhofen, so well worked out by Dr. Oppel 
of Munich, the species of which are closely represented in the 
Lias and Oolite of England.* 
The top of the Chart is devoted to a small series of Recent 
Typical Forms, placed for comparison with the less perfect fossil 
remains. Short descriptions of each group have been prepared and 
added to the Catalogue, which, it is hoped, will increase its useful- 
ness, and enhance the value of Mr. J. W. Lowry’s beautiful en- 
gravings. 
On THE Mntamorrnic Rocks AND THE GREEN Marpius or CoNNEMARA.[ 
By Prof. Harxnuss, F.R.8. , 
HE author showed, by sections and maps, that the green marbles 
of Connemara were a local and peculiar development of light- 
grey subcrystalline limestone which lies on the north side of the 
gneiss rocks of the south of the Bens of Connemara. This lime- 
stone dips conformably under these gneissic rocks. It is superposed 
conformably on quartz-rocks; and these quartz-rocks, with their 
superposed deposits, are thrown into numerous contortions in the 
Connemara country. Where they are most curtailed, the limestones 
have opened out in their lines of lamination, and into these openings 
the serpentinous matter, to which the green marble owes its colour, 
has been introduced. The metamorphic strata in the Connemara 
country appertain to the Lower Silurians. They are the equivalents 
of the Quartz-rocks, Upper Limestone, and Upper Gneiss of the 
Highlands of Scotland, described by Sir R. I. Murchison. It has 
been stated that Hozoén Canadense occurs among the green marbles 
of Connemara. ‘The structure which has given rise to this opinion 
is purely mineral, and has resulted from the deposition of Serpen- 
tine upon Tremolite and asbestiform minerals. 
CORRESPONDENCE. 
4+ —— 
EXPLORATION OF THE ‘HOYLE’S MOUTH’ CAVE, 
NEAR TENBY. 
To the Editor of the GEOLOGICAL MaGazINE. 
Sir,—In an ‘outlier’ of the Carboniferous Limestone, running 
at right angles to the ‘ saddle-back’ of Old Red Sandstone ealled the 
‘Ridgeway, is a picturesquely situated cavern, well known to visitors 
at Tenby by the name of ‘ Hoyle’s Mouth.’ Some interesting dis- 
coveries of the remains of extinct and other animals have lately been 
made here by W. A. Sanford, Esq., and myself. As your readers 
* The author stated, at the British Association at Birmingham, that he had 
determined six genera and sixteen species from the Lias alone, which nearly 
resemble oolitic forms from Bavaria. 
+ The ‘Reader,’ Sept. 16th. 
