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PROCEEDINGS OF SOCIETIES. 
of the shale is liable; and Dr. Carte has recently succeeded in procuring 
a specimen of Posidonia lateralis in the same strata which contain the 
fossil under our consideration. 
As to the geological hearing of the question, it may he observed that 
the Calp, or middle limestone rocks of Ireland, in the shales of which 
Posidonise occur so abundantly, are interposed between two blue sub¬ 
crystalline limestones, to which I have applied the relative terms Upper 
and Lower, one of them (or, perhaps, to a certain extent both) being the 
equivalent of the mountain limestone of England. These Calp strata 
consist of impure siliceo-argillaceous limestone, inter stratified with 
shales of various degrees of hardness, which frequently contain layers 
of chert, and it is in the shales and impure shaly limestones of finest 
grain that we find the matrices of the Posidonise, as appears from the 
specimens now before us. 
There are, besides, occasionally interstratified with the shales at 
Push, remarkable fossiliferous conglomerates, the pebbles of which vary 
from a size nearly half a foot in diameter to very small angular and 
rounded fragments of slate, limestone, and quartz, which are probably 
of Silurian age; and we have likewise other conglomerates, containing 
very numerous pebbles, which may possibly be regarded as carboni¬ 
ferous limestone, the appearance which they present being exactly 
similar to such recent breaches of shingle as may be observed at 
several points on the same shore. Plue fossiliferous limestone, con¬ 
taining Natico'psis Phillipsii, &c., occurs as we approach the town of 
Skerries; and I may remark that my friend Professor Jukes, who has 
minutely examined this interesting locality, is of opinion that it is dif¬ 
ficult to determine the position of this limestone in the series, owing to 
the disturbance of the strata, as, for all we can say, it may represent 
either the upper or the lower limestone, and may possibly include both. 
The Calp series, which is always of a dark gray colour, becomes oc¬ 
casionally separable into an upper and a lower portion, as in the north 
of Ireland, by means of a considerable thickness of intervening hard, 
compact, yellowish gray sandstone, an incipient representative of which 
may be observed in the Knockmaroon district of the county of Dublin. 
It may be useful to supply a few of the localities in Ireland in which 
the Posidonise have been found to occur most abundantly in the calp 
series. They have been principally obtained in the shales near JSTobber, 
at Cruicetown, and near Uavan, at Walterstown, in the county of Meath, 
also near Balbriggan, at Courtlough, and near Skerries, at Paldongan, 
as well as near Push, at Loughshinny, already mentioned, in the county 
of Dublin; but no doubt they occur in the fine-grained dark gray shales 
in many other localities, as I am informed by Mr. Jukes that they have 
been collected in the neighbourhood of Garristown, also in the county 
of Dublin. 
It would exceed the design of the present communication to enter 
into further details with reference to the remarkable geological features 
which can be studied with so much advantage in the vicinity of Rush, 
especially as we may expect that the President, as well as Mr. Jukes, 
will favour us with their views; but I may observe that probably there 
