174 
SILUKIA. 
[Chap. VIII. 
cipitated over highly inclined crystalline chloritic and micaceous schists of 
this class, which in Ireland are probably the equivalents of the crystalline 
rocks of Anglesea (see p. 35). In the central parts of the South of Ireland, or 
on the western side of the granite of the "Wicklow Hills, the limestones and 
schists of the Chair of Kildare, which are replete with fossils, or the schists 
on the flanks of the Slieve Bloom Mountains, are classed as Lower Silu- 
rian* ; so also are several masses of these rocks at Portrane to the north 
of Dublin, and especially near Pomeroy in Tyrone, the richly fossiliferous 
locality just stated to be the first clear Silurian type described in Ireland f. 
It is truly remarkable that so many of the characteristic Lower Silurian 
fossils should have been detected by the late General Portlock in this small 
tract and another, of no larger dimensions, in Fermanagh. Several of the 
Trinuclei and other Trilobites, such as Phacops, Calymene, and Illsenus, are 
identical in species with those of Caradoc (or Bala) age from Shropshire 
and Wales ; and so is it with the simple-plaited Orthidse, Leptsenge, and 
Strophomense, some Spiral Shells, and many Orthocerata (Plates I.-XI.). 
Commingled, however, with these are peculiar forms which were first made 
known from this district, and are very rare indeed in any other tract of 
the British Isles. Such, for example, are the Trilobites figured in 
the Tenth Chapter, the Eemopleurides, Harpes, Amphion, and Bronteus. 
Such also are the smooth forms of Asaphus, called Isotelus by American 
authors, which in Ireland, and on the other side of the Atlantic, are very 
abundant, whilst they are exceedingly rare in Wales or England, and are 
not known on the Continent 
In Wexford, Waterford, and at the Chair of Kildare, the older strata 
have been so much disturbed and insulated that it is difficult to detect 
* It is believed that the schists of Down may experienced Irish geologist, Mr. John Kelly, 
prove to be of the sameage as the graptolite-schists J A new species of Phacops (P. Nicholsoni, 
of the opposite Scotch counties of Wigton, Gallo- Salter) has been found in these Caradoc rocks of 
way, Ayr, &c. Tyrone (Quarterly Journ. Q-eol. Soc. vol. xxii. 
t I examined this tract in company with that p. 486). 
Fossils (29). Lower Silurian Trilobites, Ireland. 
1. Asaphus 
(Isotelus) gi- 
gas, De Kay; 
anditslabrum. 
