560 Mr. Maclauchlan's Notes on Fossils collected in PembroTceshire. 



mens obtained by Mr. Murchison from the Caradoc sandstone, at Little London, 

 May Hill, and Gorton near Presteign. See Silurian system, pi. 20. fig. 19. 



This conglomerate commences at Dinas Head, and crossing Newport Bay, con- 

 tinues to the hill above Trewiddel, near Cardigan, and probably further. 



It does not appear to be disturbed by igneous rocks. 



Trappean ash is found near the conical elevations of intrusive greenstone at 

 Penbury Hill, two and a half miles north- north-east of St. David's, Llanllawer, 

 two miles south-east of Fishguard, and Carningley, one mile south of Newport. 



It is provincially called toughstone, and is worked as a building material, being 

 soft when first raised, but hardening by exposure to the air, and very durable. 

 Though the summit of the principal elevation of the Pembrokeshire chain is not 

 trap, but roofing-slate, yet beds of trap extend nearly to the top, and are continuous 

 apparently throughout the district, having masses of more decided greenstone oc- 

 casionally protruded through them. 



These beds may be traced to Plumstone Mountain, five miles north-west of Ha- 

 verfordwest, and to St. David's Head, and thence through "The Bishop and his 

 Clerks Rocks," and the dangerous rocks called "The Hats and Barrels," to the 

 rock of " The Smalls Lighthouse." 



On the north-east of the chain, at Whitchurch (Eglwyswen), six miles north- 

 east from Newport, on the east at Llanfirnach (Llanfrynach, Ord. Map), and on 

 the south at Llanglywdwen, are beds of a dark carbonaceous shale, which appa- 

 rently overlie and mantle round the trap rocks, yet still preserve the northerly 

 dip. These beds have been worked unsuccessfully for culm, and are accompanied 

 by lead veins, one of which at Llanfirnach has proved to be profitable. 



At Llanglywdwen Bridge are indications of copper, and a considerable bed of 

 limestone is in contact with the lode. 



Mineral veins were also observed along the coast, from Newgate in St. Bride's 

 Bay to St. David's Head. 



At Fishguard and Strumble Head are basaltic columns, and at Llanwnda a 

 jasper vein, and veins of green compact felspar. 



May 1841. 



