On the Pdh'Jeontolocpj of County Dahlia. 165 



Conchifera. 



Modiolopsis and Orthonota, species undetermined. 



N ucleobranch lata (Heteropoda). 

 Bellerophon perturbatus. 



Annulosa : EeMnodefmata. 



Crinoid joints and stems. 

 Cystidean] plate. 

 Glyptocrinus ; portion of column. 

 Palseasterina 1 starfish. 



Annelida. 

 Tentaculites Anglicus. 



Crustacea : Phyllopoda. 

 Beyrichia complicata. 



Trilobita. 



**Calyniene brevicapitata. 



Homalonotus bisulcatus ? 

 Lichas laxatus. 

 *Phacops Brongniarti. 

 Trinucleus concentricus. 



North of Dublin, Lower Silurian fossiliferous rocks of Caradoc- 

 Bala age again appear on the shore at Portrane, and at Lambay 

 Island, County of Dublin ; at both these places the lithological 

 character of the rocks, black slates and dark grey limestone, with 

 their contained fossils, are precisely identical. These black 

 slates may be observed on the Portrane shore a little south of 

 the first martello tower from the coastguard station, and on the 

 east side of Lambay Island, north of Kiln Point. From them 

 have been obtained one species of Graptolite, Diplograpsus 

 pristis, having a central axis with a double series of cells arranged 

 on either side. 



The Silurian limestone is well exposed in prominent cliffs on 

 the Portrane shore, at several places between the first and second 

 martello towers, south of the coastguard station. These rough 

 crags have all the appearance of an ancient coral reef; the chain 

 coral, Halysites catenidariiis, Heliolites, Favosites, and Cyatho- 

 phyllum, occur in profusion, being weathered out by sea and 

 atmospheric action. 



N 



