Fearnsides, Elles, Smith — Palceozoic Rocks of Fomeroy. 99 



their Haverfordwest fossils, made a re- examination of Portlock's type 

 specimens, and, in so doing, were able to refer the Trilobites of the 

 district to the upper division of their Bala rocks, and thereby to 

 correlate Portlock's Caradoc sandstone with what has now become the 

 Ashgillian series. 



In 1896 the officers of the Irish Geological Survey returned 

 to the area, and, as represented by McHenry and Egan, collected 

 such considerable suites of fossils that the Survey palaeontologists 

 were able definitely to identify several zones of Eirkhill or Llandovery 

 rocks, as well as to confirm the Ashgillian age of the great bulk of 

 the Trilobite-bearing sandy beds. The fossils collected at this time 

 are now preserved in the collections of the Irish Survey ; but the 

 results of these researches have not been published. 



The actual Lower Palaeozoic area is more or less triangular in 

 shape, with sides varying between three and four miles in length. 

 The base faces to the north, and is rather irregular. Along it the 

 lowest members of the fossiliferous series adjoin a very variable mass 

 of ancient hornblendic or granitic rocks, while along the southern, 

 south-eastern, and south-western sides, the various members of the 

 series are unconformably overlain by the characteristic green and red 

 sandstones and conglomerates of the local Old Eed Sandstone. 



Unfortunately the district is much diift-covered ; and its scenery is 

 dependent upon the irregular distribution and variable character of its 

 esker-like mounds of drift. These consist of porous semi-stratified 

 sands and gravels ; and only where the usually over-full streams have 

 deepened their valleys down to the solid rock below are the 

 interesting lower Palaeozoic rocks exposed. No large amount of stiff 

 boulder-clay or till was met with ; but the gravel contains many 

 travelled boulders of large size which, if of sedimentary origin, often 

 contain good fossils. 



These gravel-ridges are] occasionally from 100 to 150 feet high, 

 and in places are so steep-sided that they fail to support more than a 

 very scanty covering of vegetation. Under these conditions, all 

 evidence as to structure or succession of the rock-series must be based 

 upon scattered exposures, or upon palaeontology, and a detailed 

 comparison of the faunas of the various rock-beds with those observed 

 in other and more openly exposed districts. The exposed areas and 

 the detailed succession afforded by each are indicated upon the map, 

 and in the absence of a sufficiency of place-names will only be 

 alluded to incidentally in the body of the paper. 



The following sub-divisions of the sedimentary series have been 



X'l 



