94 STRATIGRAPHICAL GEOLOGY 



determined, the difficulty being that the rocks are so much folded, 

 contorted, and faulted that it is almost impossible to trace particular 

 beds in the mass of slates. Few fossils except graptolites have 

 been found, and these occur in definite bands of a more earthy 

 kind of slate than the rest, so that, as Dr. Marr observes, " whether 

 these beds are of the same age as the black glossy unfossiliferous 

 slates, or whether they are newer beds folded as synclines among 

 these slates, yet remains to be ascertained." 



The only locality indeed where graptolites of Tremadoe species 

 have yet been found is Barth near Keswick, where the following 

 species were obtained by Miss G. L. Elles 18 in 1898 Bryograptus 

 Kjerulfi (see Fig. 15m), B. ramosus, B. Callavei, Chonograptus tenellus, 

 and Ch. flexilis. 



The greater part of the Isle of Man is occupied by a similar 

 series of slates and grits, now known as the Manx slates. These 

 have been divided by Mr. Lamplugh into three portions which 

 seem to be consecutive, though no recognisable fossils have been 

 found in any of them, and the crush-phenomena produced by 

 lateral compression are even more strongly developed in that island 

 than in Cumberland. 19 



The subdivisions traced by Mr. Lamplugh strike from N.E. to 

 S.W., and the Lonan flags on the eastern side are believed to be the 

 lowest ; these seem originally to have been flagstones, mudstones, 

 and shales, but are now hard, cleaved, crumpled, and frilled rocks. 

 North-west of them is a band of quartz-veined, thin-bedded grits 

 (the Agneash grits'), and west of them are the Barrule slates, a mass 

 of dark-blue slaty rocks, which closely resemble the Skiddaw slates. 

 Of the Lonan flags Mr. Lamplugh observes that lithologically they 

 have a close resemblance to the Bray Head Series described below. 



4. Ireland 



So far as present knowledge extends Cambrian rocks only occur 

 in the south-east of Ireland in the counties of Dublin, Wicklow, and 

 Wexford. The facies is one of grits, flagstones, and shales like that 

 of Wales, but the base is not exposed and none of the Welsh fossils 

 have yet been discovered in the Irish area. The rocks are indeed 

 so cleaved and altered by metamorphic agencies that until recently 

 it has been an open question whether they were of Eparchsean or 

 Cambrian age. 



The determination of their age rests mainly on the discovery 

 of their characteristic fossil Oldhamia (see Fig. 12) in rocks of 

 Cambrian age elsewhere. It is certainly curious that Oldhamia 

 should not have been found in the Cambrian of Wales, but in the 



