150 -ME. F. E. COWPEE EEED OK THE GEOLOGY OF [May 1895, 



coast, and to investigate the characters of both the contemporaneous 

 and intrusive igneous rocks in the field and laboratory. To peno- 

 logical questions, therefore, special attention has been paid. 



The area with which this communication deals extends from 

 Newport in the east to the western side of Strumble Head in the west, 

 and lies north of a line drawn from Pwll Crochan to Cilgwyn, and 

 passing through St. Nicholas and Llanllawer. This narrow strip of 

 country, it will be noted, approximately coincides with the strike of 

 the beds. (See Map, PI. V.) 



II. Steuctttre op the Disteict. 



The general geological structure is readily understood on ex- 

 amining the 1-inch Geological Survey map. West of Fishguard 

 town Llandeilo rocks, with apparently a general east-and-west strike 

 and northerly dip, occupy most of the ground. A conspicuous wedge- 

 shaped outcrop of ' felspathic ashes and traps ' runs from the north- 

 east point of Pen Caer in a south-westerly direction past Goodwick 

 to a point near St. Nicholas, where it tapers out and disappears. 



Other masses of similar rocks are indicated at Porth Sychan, on 

 Castle Point, on the coast towards Dinas, as far as Aber Eiehard ; 

 and a band extends from Bwlch Mawr in the west to a point south 

 of Aber Rhigian, while an isolated patch is seen at Cam F,foi. 



Large masses and bands of intrusive ' greenstone' are marked in : 

 one enormous mass extends along the north coast of Pen Caer in a 

 broad belt, and sends off a strong spur to the south through 

 Llanwnda. Another considerable mass crosses the centre of the 

 headland from Pwll Deri to Y Garn ; while east of the town of 

 Pishguard, and farther on towards Newport, sheets and lenticular 

 patches range more or less parallel to the strike of the strata into 

 which they have been intruded. 



The slaty beds are stated to be of Llandeilo age, and ' altered 

 Llandeilo' rocks form two contact-zones. Such is the information 

 that we gather from a brief examination of the Geological Survey 

 map. 



In the sketch-map accompanying this paper (PI. V.) some slight 

 modifications have been found necessary. Firstly, in the place of the 

 zone of ' altered Llandeilo ' on the north of the Pwll Deri — T Garn 

 intrusive mass, a tract of volcanic rocks is inserted. A small patch 

 of similar rocks has also been found on the northern side of Porth 

 Melyn, near Pwll Deri, in the midst of the ' greenstone.' Secondly, 

 the ' interbedded felspathic traps and ashes' of Castle Point, Pish- 

 guard, have been found also on the western side of the harbour and 

 crop out again at Bigney, in Cwm Brandy, in Cwm Bach, and on 

 Manorowen Hill; and possibly the conspicuous rugged knobs tf 

 Cam Llys, \ mile S.E. of St. Nicholas, are a continuation of the 

 same beds. But the great variation in volcanic beds of the same 

 geological horizon, when traced along their strike, is markedly 

 illustrated in this area, and renders the identification and correct 



