Vale of the Towy, and Golden Grove, as seen from Dynevor Park near Llandeilo, sketched by Mrs. Murchison. 



CHAPTER XXVIII. 



CAERMARTHENSHIRE. 



Course of Upper and Lower Silurian Rocks maintained by superposition and or- 

 ganic remains. — Great changes in lithological structure. — Lower Silurian 

 where lest developed — in parts affected by slaty cleavage. — Fine exhibition of 

 Llandeilo flags, their passage into Cambrian System. — Change of strike as 

 the strata pass into Pembrokeshire. — Cambrian Rocks .— Trap and Altered 

 Rocks.— Mines, $c. (PL 34. figs. 1 to 11.) 



Silurian Rocks in Caermarthenshire . 



Upper Silurian rocks, similar to those of Brecknockshire, are prolonged into Caer- 

 marthenshire with precisely the same relations to the overlying red sandstone ; whilst 

 the Lower Silurian Rocks, of which the traces are so imperfect both in Radnorshire 

 and Brecknockshire, reappear in as great force as in any parts of Salop, Hereford, or 

 Montgomery ; the Llandeilo flags, in particular, having their fullest development in this 

 and the adjoining county of Pembroke. A good natural transverse section of the upper 

 group is exposed in the narrow valley of Cwm-dwr 1 , already noticed in describing the 

 tilestones of the Old Red System. 



1 In the prolongation of the escarpment of Mynidd Epynt and Mynidd bwlch-y-groes. See p. 181 et seq. 



