262 



[Nov. 29, 



Section V. 



The Vyrnwy River, 1 mile S. W. of Meifod, to Hirnant, about 2 miles S. of 



Llangynog. 



Mean Direction of the line of Section, S. 40° E. to N. 40° W. 

 Horizontal base lOi miles. 



S.E. N. 25° W. 



S. 250 E. 



•^ Alt-y-goeth. 



This section commences with the upper Silurian rocks (a), which 

 extend southward from the Vyrnwy river to the Severn. It is fol- 

 lowed by rocks of the lower series (b, h\ h"\ containing calcareous 

 bands (\, X', X", X'''). The lower fossiliferous bands near Meifod 

 agree generally in their fossil species with the limestone of Bala, 

 and with the fossiliferous beds on the line of the Teirw river oc- 

 curring below, and associated with the porphyries, as described in 

 Section IV. The line of section afterwards again cuts the over- 

 lying upper Silurian rocks (c, c', c"\ a little within the line of 

 their northern boundary. The lower system appears to the south 

 of Llangynog, alternating with beds of cotemporaneous porphyry. 



Section VI. 

 Pen-y-Craig, 3 miles S.W, of Meifod, across the Bechan River to Doto- 



BRANUCHAF. 



Horizontal base 1^ miles. 



9 N. ISO vv. 



At Pen-y-Craig, south of Mathyrafal, just at the base of the 

 overlying upper Silurian flagstone (a), there is a higher fossilifer- 

 ous group {fx) than any which has yet been described. The upper 

 part of this passage group consists of calcareous shale, and the 

 lower part of conglomerate, sandstone, and limestone. Further to 

 the north we have the lower series of the ordinary type in the 

 neighbourhood of Meifod, with two calcareous and fossiliferous 

 bands. 



[Note on the Fossils of the Limestone of Pen-y-Craig. — Lepfcena tenui- 

 striata, which vi^as abundant in the lower fossiliferous group (\), is not seen in 

 the limestone. Corals are very abundant, and are nearly the same with those 



