Chap. VIII.] UPPER SILURIAN IN IRELAND. 177 
tified volcanic ash and bosses of igneous rock, is there found to be charged 
with typical Wenlock fossils. These are Euomphalus funatus and other 
species of that genus, Spirifer bijugosus, Ehynchonella nucula, Orthis 
elegantula, Atrypa reticularis, Proetus latifrons, with numerous Corals, 
The Sibyl Head (seen from the Western Ocean). 
(Sketched by Mr. Du Noyer, of the G-eological Survey.) 
The strata rising up to the highest point, Sibyl Head, consist of Upper Old Red 
sandstone and conglomerate. The lower ledges are Silurian. 
including the Chain-coral, also the Trilobites Phacops caudatus and En- 
jcrinurus punctatus. In the same strata we also find Chonetes lata in 
abundance, whilst in England it is the typical fossil of the Upper Ludlow 
rock. 
The beds which contain contemporaneous volcanic grit, and occasion- 
ally intrusive greenstones, are overlain by strata which are best exposed 
inland ; and in these (as between Doonquin and Croagh-marhin) there are 
many true Ludlow rock and Aymestry fossils— such as Pentamerus 
Knightii, Ehynchonella Wilsoni, Eh. navicula, Avicula reticulata, &c, 
together with Calymene and the small Lichas angiicus. In truth, how- 
ever, the geologist would scarcely be able to draw those distinctions 
between the Wenlock and Ludlow rocks which are traceable in Siluria, 
but for the occurrence of a band of red slate and a thick development of 
fucoidal sandstones, which here form the base of the Ludlow rocks. These 
fucoidal strata are well seen in Clogher Bay and Smerwick Harbour, their 
physical relations and organic characters having been traced out by 
! Messrs. Du Noyer and Salter. In the overlying beds with Pentamerus 
| Knightii and Cardiola interrupta, there are numerous species of Corals, 
