10 Mr. De la Beche on the Geology of Southern Pembrokeshire. 



from Druson Haven to Broad Haven,, a section of the greywacke is presented 

 by the coast. On both sides of Druson Haven the strata are much contorted. 

 (See PI. n. fig. 1.) From thence to Broad Haven there are both thick and 

 slaty beds, though usually in the Haverfordwest district the greywacke is slaty. 

 The southern limits of this district will best be traced on the map. (See PI. I.) 

 Near the eastern extremity of the southern boundary-line, between Lether- 

 gloyn and the river near Canaston, the junction of the greywacke with the 

 superincumbent old red sandstone is tolerably well defined. 



(B) Greywacke South of the Coal-hasin. 



On the southern side, and also round the eastern extremity, of the trap- 

 ridge extending from Bolton Beacon to Benton Castle, a peculiar rock occurs, 

 which may be considered as a neutral one, between greywacke and old red 

 sandstone, having more the character of the former than of the latter, though 

 seldom acquiring the slaty appearance of the greywacke occurring to the north 

 of the Coal-basin. 



This rock commences in a point near Tiers Cross, and gradually widens 

 towards the west. Prom Tiers Cross it is bounded on the south by genuine 

 old red sandstone, into which it passes so gradually that no line of separation 

 can be drawn between them. The boundary, however, may be considered as 

 passing through Redstock, and thence southwards of Rosemarket to Llan- 

 stadwell. Leaving Johnston for Milford, yellowish-brown beds of sandstone, 

 which may be termed friable greywacke, are met with, dipping from the trap. 

 Loose sandy beds occur not far from Johnston on the road to Rosemarket, and 

 at a little distance from the trap on the road between Rosemarket and 

 Waterless. At a point where a small rivulet crosses the last-mentioned road, 

 beds of greywacke appear dipping to the west. At Milton, between Rose- 

 market and Pembroke Ferry, a few thin beds are seen dipping to the south- 

 east, at an angle of 45°, which have more the character of old red sandstone 

 than of greywacke. At Burton the rock is principally of a brownish-gray 

 colour ; but two or three red strata traverse the garden of the parsonage. 

 The same rock, with a few red strata occurring here and there, continues nearly 

 to Benton Farm. The beds are sometimes of tolerable thickness, sometimes 

 coarsely slaty, and frequently micaceous. The small peninsula between West 

 Lenion and Pembroke Ferry consists of the same rock, as does the entire penin- 

 sula of Cosheston. Very few red strata are observable between Cosheston and 

 Lawrenny Ferry. The dip at Cosheston is to the south-east : that on the south 

 side of Lawrenny Ferry is to the east, at an angle of from 20° to 30°. The 

 western part of the Lawrenny peninsula is also of this rock, mixed with some 



