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



that of Pembroke, and that of Orielton : the first lying to the north of Mil- 

 ford Haven, the two latter commencing on the opposite shore, and being 

 separated from one another by a trough of carboniferous limestone. 



Milford Subdivision. 



The coast of St. Bride's Bay, from the trap of Millhaven to that of Marloes, 

 affords a section of the western part of this subdivision. This sandstone is 

 bounded on the north, from Millhaven to Tiers Cross, by a mass or dyke of 

 trap ; and on the north-east, from Tiers Cross to Llanstadwell, by the rock 

 resembling greywacke. On the south, from St. Ann's Head to Llanstadwell, 

 it is terminated by Milford Haven. Skokham Island is a continuation west- 

 ward of the sandstone which extends from Dale to St. Ann's Head. 



The principal dip of the sandstone-beds in this subdivision is to the south. 

 At their junction with the trap, near Millhaven, they are contorted. (See PI. II. 

 fig. 3.) From thence to St. Bride's they gradually acquire a gentle dip to 

 the south, of from 15° to 20°. At their junction with the trap, near Mosely- 

 wick, they are highly inclined ; which is mostly the case, indeed, with the 

 beds in this subdivision. 



In different places the strata vary very much as to hardness. They are some- 

 times marly, and in other cases they consist of a very compact siliceous grit. 



To this subdivision it will be most convenient to refer the beds upon which 

 the coal-measures rest near Langum, at the north-east corner of the range of 

 trap extending from Bolton Beacon to Benton Castle. They have the cha- 

 racter rather of old red sandstone than of greywacke, though a few strata 

 resembling the latter are mixed with them. The same beds cross the point 

 near Langum Ferry, and reappear in the eastern part of Lawrenny. 



Pembroke Subdivision. 



The principal part of this subdivision is contained in a narrow band of sand- 

 stone running nearly due east from Milford Haven to Caermarthen Bay, and 

 dipping on either side beneath cai'boniferous limestone. The Ridgeway, on 

 the road from Pembroke to Penally, commanding fine views of the surrounding 

 country, is the highest hill in this subdivision. The sandstone of this band 

 appears again to the west in two small peninsulas on the southern side of Mil- 

 ford Haven. 



The sandstone here treated of closely resembles that of the Milford subdi- 

 vision ; but some near Patterchurch approaches in character to the rock resem- 

 bling greywacke. A small-grained compact quartzose conglomerate appears 

 in the neighbourhood of Penally. There occurs in several places on the top 



