Vol. 65.] EOCKS OF THE TOTJEMAKEADY DISTRICT. 131 



becoming somewhat amygdaloiclal in places. The rocks in 

 its immediate neighbourhood are not well seen, but it is 

 probably intrusive along the line of junction of the Llandeilo 

 Beds with the (?) Bala conglomerates. 



(2) A second band of very similar rock (133), often highly amygda- 



loidal, is traceable for a distance of about 100 yards through 

 the coarse Arenig grits north of Mount Partry. The rock is 

 exposed in the stream-bed and at spots near the right bank, and 

 can be followed for some distance beyond the left bank. A 

 closely related rock (245), showing numerous small pyroxenes 

 in a hand-specimen, occurs about 300 yards north-west of 

 the Monastery. A further exposure of dark andesitic rock 

 (95) is found on the south-eastern slopes of Mount Partry, 

 intrusive among the coarse felsitic tuffs which make up the 

 bulk of the hill. 



(3) A small intrusi6n of a somewhat different type of rock (292), 



full of small amygdules, occurs north of Gortanalderg near the 

 western boundary of the red felsite-mass, and a large mass 

 of a similar nature (294) at a point about 500 yards to the 

 north-east, close by the east-and-west road. 



(4) Several exposures of what are probably two intrusions (140 & 



240) are seen south-east of the triangular area of Arenig rocks 

 between Gortanalderg and Drumcoggy Bectory. The rocks are 

 grey-green and very amygdaloiclal in places ; though occurring 

 close to the Arenig Beds, they are intrusive in the felsite. 



(5) A small patch of a fine-grained rock of andesitic type occurs 



immediately west of the augite-felsite at Shangort. 



(c) The Hornblende-Larnprophyres and Dolerites. 



These rocks form a series of small but interesting intrusions, 

 principally distributed round the margin of felsite-masses. 



Hornblende-lamprophyres are met with at the following 



points : — 



(1) About 150 yards north of Gortanalderg (21). The rock here 



forms a more or less circular intrusion, some 50 yards in 

 diameter, in the Llandeilo tuffs, which appear to be somewhat 

 altered near the junction. 



(2) Half a mile farther north-north-eastwards, near the left bank 



of Stream P, is a second small, more or less circular intrusion 

 (43), measuring only some 10 yards across. This is also com- 

 pletely surrounded by Llandeilo tuffs. 



(3) Two little patches, each having a visible diameter of only a 



few yards, are exposed near the upper part of Stream C, west 

 of Gortanalderg. These may be continuous with one another. 



(4) Intrusive in the triangular area of Arenig grits, cherts, and 



tuffs, nearly a mile west-south-west of Drumcoggy Pectory, is 

 another small patch of similar rock (168). 



