A. B. Badger — Exposures of Quartz- Felsite, Carnarvonshire. 261 



Two other specimens in Wallieli's collection certainly come from 

 a different horizon, and their mode of preservation is not the same. 

 One is the imperfect valve of a species of Halohia comparable with 

 II . charhjana, Mojs., which has been recorded from the Trias of Eotti 

 and Sumatra ; ^ it occurs in a black shaly limestone. The other is the 

 internal cast of an ammonoid almost wholly replaced by crystalline 

 calcite, but showing in one part the suture-line, the characters of 

 which, so far as they are visible, suggest that it may be referred to the 

 genus Ptychites, and the shape of the shell much resembles that of 

 Ft. rugifer, Oppel. It is evident, therefore, that the Trias also occurs 

 near Muktinath. 



V. — Pkeliminaet Note ok some Unrecorded Exposures oe the 



Quartz-Felsite in I^okth-'West Carnarvonshire. 



By A. B. Badger, M.A., B.Sc. 



DURIjSI'G an investigation of the rocks of North-'West Carnarvonshire 

 older than the Llanberis Slates, the detailed results of which 

 I hope soon to publish, I have discovered certain exposures of 

 quartz-felsite which are not marked as such on the maps of the 

 Geological Ordnance Survey, nor have been described, as far as I know, 

 by other observers. 



Reference to maps 75 N.W., 78 S.W., and 78 S.E. of the 1 inch 

 Geological Survey, or to Sheet 7 of the Geological Index Map, will 

 show that in the area stretching from Bangor and Bethesda on the 

 north-east to the Vale of Nantle on the south-west two bands of 

 quartz-felsite are marked, the one extending from Bangor to Car- 

 narvon, the other from the Penrhyn Slate Quarry through Llanberis to 

 the village of Llanllyfni. As is well known, these rocks have been 

 variously regarded as of Pre-Cambrian, early Cambrian, and Post- 

 Cambrian age. 



The exposures which I desire to record lie to the west of the eastern 

 band of felsite, and proceeding generally from north-east to south-west 

 occur at the localities named below. 



1 Inch 

 Locality. Geological Map. 6 Inch Ordnance Map. 



(1) Farm of Ty'n y caeau 78 S.E. Carnarv 



(2) Gwirfai River, near Bontnewydd... 78 S.W. 



(3) Near Gadlys Farm ..." ... ,, 



(4) Near Llanwnda Railway Station ... ,, 



(5) GlynllifonPark 75 N.W. 



(6) Brynmawr Farm ... ... ... ,, 



(7) East of Llanllyfni 



onsMre, XII, N.W. 

 XV, S.E. 



XX, N.E. 

 XX, S.E. 

 XX, S.E. 

 and XXI, S.W. 



( 1 ) Tifn y caeau Farm. — This locality lies about 2 J miles to the 

 north-west of Penrhyn Quarry, the most northerly point at which the 

 eastern band of quartz-felsite has been found hitherto. The outcrop 

 is about 330 yards in length and 50 yards in breadth at its widest. 

 It strikes 60° east of north and forms a low ridge. On the north-west 



1 Volz: Zeitschr. deut. gaol. GeselL, vol. li (1899), p. 35, t. i, figs. 12, 13. 



