536 Scientific Proceedings^ Royal Dublin Society. 



This probably indicates, as Matley points out,' the proximity of the latter 

 locality to a river mouth. It would explain the considerably greater thick- 

 ness of the zones in the south. 



The present paper deals with the following parts of the section (see map, 

 - PI. XXXV):— 



(1) From the southernmost exposure to the bathing-place north of 

 Rush, including the Eush Slates, Eush Conglomerate, with its overlying 

 Limestones, Carlyan Eooks and Kate Eooks ; 



(2) the Lane Limestone and Conglomerate, and the Holmpatrick 

 Limestone at the northern end of the section, near Skerries. 



The map is modified from Matley's maps of the outcrops. ^ The lower 

 portion shows (1) the Eash Slates to the south and east of Eush. They dip first 

 east, then north. Prominent fossiliferous limestone bands are marked (after 

 Matley) Rib, E 4 a, E 6 b, and E 8 a. The faults are of insignificant throw. 

 Next in order, northwards, comes (2) the Eush Conglomerate Group (more 

 deeply coloured). This includes the beds to which Matley attached the 

 symbols E 9, E 10, and Ell. It consists of frequently recurring beds of 

 calcareous conglomerate, sandstone, shale, and limestone, dipping steeply to 

 the north. Upon these lie (3) the Supra-Conglomerate Limestones forming 

 the southern boundary of the entrance to Eush Harbour. These and the 

 upper conglomerates are much faulted, but the displacement is never more 

 than a few feet. The succession is broken here by sand and water. North 

 ^of Rush Harbour are (4) the Carlyan Limestones. These dip north at a 

 \ low angle, are often pebbly and sometimes oolitic. After a stretch of sand 

 occur (5) the Kate Limestones, dipping mostly northwards, but much folded. 

 Chert layers are common here, and pebbles r-are. Just north of these rocks a 

 mile and a half of the coast-line has been omitted from the map. The next 

 beds which concern us occur half a mile north of Loughshinny (Lane Lime- 

 stone). They are bounded on the south by a branched fault of considerable 

 throw. The dip is nearly north and at low angles. A coarse uniform 

 conglomerate (Lane Conglomerate, coloured more deeply) succeeds this 

 conformably, and is overlain conformably by the Holmpatrick Limestone, 

 both dipping at low angles nearly northwards. The Holmpatrick Limestone 

 is much dolomitized in the lower half, and contains oolitic layers near 

 the base. 



Before giving details of the present work, it will be useful to review 

 the state of the problem, in order to exhibit the difficulties which require 

 clearing up. 



' Quart. Joiirn. Geol. Soc, vol. Ixiv, 1908, p. 434. ^ loc. cit. 



