Vol. 56.] THE SILURIAN SEQUENCE OF EUAYADEE. 107 



The peculiar orange weathering of the grits, due to the presence of 

 limonite, is still retained and forms a predominant feature. ' 



Fossils may be found in one band about 100 yards south of the 

 cairn. They are impressed as a rule into the grit- surfaces, and 

 are in a fair state of preservation. The following species of grapto- 

 lites were obtained : — 



Monograptus Sedgwickii. 



spinigerus, JN T ich. 



lobiferus. 



harpago (?) Toruq. 



■ involutes, Lapw. 



Proteus, var. 



Cling ani, Oarr. 



decipiens (?) Tornq. 



Monograptus convolutus. 



, Tar. spiralis, Grein. 



Bastrites hybridus (?) Lapw. 

 Diplograptus sinuatus. 

 Didyonema delicatulum, Lapw. 



corrngatellum, Lapw. 



Calyptograptus digitatus, Lapw. 



And in addition to the crinoid-rings in the black-banded grits 



occurs Favosites gothlandica, Eougt. 



The Gafallt Shales (Bb 2 ) which succeed the foregoing group 

 have a thickness of at least 250 feet. They form the long dip-slope on 

 the north side of the hill, and their maximum thickness may be mea- 

 sured with approximate accuracy. They consist of pale bluish-grey, 

 greenish-grey, and green shales, and flaggy shales, all highly cleaved. 

 They are striped with thin arenaceous bands which may be of hard 

 grit or soft, rotten, brown or felspathic sandstone. They are mono- 

 tonous in the extreme ; for, with the exception of worm-markings, 

 they are apparently barren of fossils. Their interest, however, lies 

 in the fact that they form a transitional zone between the under- 

 lying rocks and the llhayader Pale Shales (C). 



(2) Corn Gafallt. 



This section (fig. 12, p. 106) is taken about | mile east of the 

 preceding section. The Lower Conglomerate (BaJ has here a 

 thickness of only 150 feet, and is separated from the Upper 

 Conglomerate by a hollow, which answers to a vertical thickness 

 of about 60 feet. This groove, we may assume, is the representa- 

 tive of the Intermediate Shales {Ba 2 \ but unfortunately no 

 exposures are to be found. The hollow, however, is well marked, 

 it may be traced both eastward and westward, and is found always 

 separating the Upper and Lower Conglomerates. The Upper 

 Conglomerate (Ba 3 ) is about 200 feet thick at this point, while 

 100 yards or so to the westward it reaches very nearly 250 feet. 

 This sudden increase may be due possibly to faulting ; but there is 

 no means of proving this. 



The Monograptus -SedgivicJcii Grits (Bb x ) maintain a fairly 

 constant thickness : bat very few exposures of the Gafallt Shales 

 (Bb 2 ) occur along the northern slope of the hill. Where beds are 

 revealed, they are seen to dip at about 20° north- north-westward, 

 the constant inclination of the whole series along this section. 



As we pass eastward from the last section the beds gradually 

 swing round to the northward. The puddingstone-bed, which can 

 be easily followed, sweeps round at the end of the hill until it runs 

 almost due north. It may be traced to a short distance above the 



