Lower Palaeozoic Rocks of the South-East of Ireland. 565 



The colours of these rocks are dull green and dull red, of many various shades, 

 sometimes passing into yellow, brown, or purple. 



Great beds of dull yellow or brown quartz rock are locally interstratified 

 with them. 



This series contains a peculiar, although a very scanty, assemblage of fossils, 

 consisting of some small impressions of radiated Zoophytes, called Oldhamia by 

 Professor Edward Forbes, and some very well-marked holes and impressions, 

 left by Annelids of two kinds, one called Histioderma by Dr. Kinahan, and the 

 other Arenicolites by Mr. Salter. 



2. The Cambro- (or lower) Silurian rocks are likewise many thousand 

 feet in thickness, consisting principally of an earthy clay slate, of a dark gray, 

 blue or black, colour, occasionally becoming green or red, or variegated- 

 Thin fine-grained gritstones are often interstratified with these slates, and occa- 

 sionally a small assemblage of more thickly bedded grits may be seen, never, 

 however, attaining the dimensions of those which are frequent in the Cambrian 

 rocks. No beds of quartz rock are to be found interstratified with the Cambro- 

 Silurian series, but large masses of contemporaneous trap (chiefly felstone) ac- 

 companied by beds of trappean ash, are to be seen in it, associated with other 

 igneous rocks of an intrusive character. 



Speaking generally, the Cambro-Silurian rocks of the south-east of Ireland 

 contain but few fossils, but in particular localities fossils occur rather abundantly: 

 those localities always being in situations which show them to belong to the 

 central or upper parts of the series rather than to the lower. 



The species of fossils found are such as prove the fossiliferous beds to be 

 of the same age as those of the Bala and Caradoc series of North "Wales, tlie 

 paljeontological evidence being thus in precise agreement with that to be de- 

 rived from lithological structure. 



The following lists of fossils will demonstrate this: — 



1. From Slieveroe, near Eathdrum, county of Wicklow. 

 Stenopora fibrosa. Tentaculites annulatus. 



Chajtetes petropolitanus. Calymene Blumenbachii. 



Orthis testudinaria, 0. Actonijc. Homalonotus bisulcatus. 



Leptaina sericea. Beyrichia complanata. 



Euomphalus perturbatus. Trinucleus concentricus. 



VOL. xxiir. 4 E 



