THE GLACIAL DEPOSITS OF WESTERN CARNARVONSHIRE. 27 



recently eroded channel at the base of the rocky ridge which bounds the bay on its sea- 

 ward side. 



Following the coast-line south-westwards we come next to Porth Uchain, a very 

 small inlet with rocky cliffs at the sides attaining a height of about 40 feet and capped 

 by yellowish weathered clay. Opposite the middle of the bay the Lower Boulder Clay 

 appears and forms the lower part of the cliff; above the clay there is a slope which is 

 grassed over. 



From this point to the next bay — Porth Caiman — the cliffs are rocky and have a 

 steep slope to the sea. The bay which follows is broad, and the northern portion of it 

 is sometimes known as Porth Penllech. Here the cliff attains heights of 30 to 40 feet. 

 In places the lower part of the cliff is rocky, but at one spot rather stiff dark grey 

 boulder clay with many included stones is seen. This becomes yellowish and friable 

 where weathered. It probably represents the Upper Boulder Clay, for a little further on 

 it is seen to overlie gravel and boulder gravel. 



The remaining portion of the bay is usually called Porth Colman. At its southern 

 end the base of the cliff is formed by rock in situ for heights varying up to 18 or 20 

 feet. Along a part of this shore a rock-shelf or platform is seen, reminding one again 

 of the raised shore platform described by Messrs Wright and Muff as occurring on 

 the south coast of Ireland (fig. 2). The platform lies 10 or 12 feet above the modern 

 beach and slopes gently upwards to about 15 feet, where it disappears under the Drift 

 deposits. It has an exposed breadth of 6 yards or so in places. The surface of the 

 platform is covered with lichens or partly grassed over. At its inner end it is covered 

 by bluish-grey Boulder Clay containing shell-fragments. This is succeeded above by 

 the Upper Yellowish Stony Clay. As we pass towards the middle of the bay the plat- 

 form disappears and the cliffs show steep rocky faces with a capping of Drift forming a 

 gentle slope landwards. Near the middle of the bay is a remarkable little inlet with 

 steep canon-like sides from which a small stream issues. A few yards up this inlet 

 the stream is seen to descend by a waterfall over rock to the level of the beach. 



The following erratics were obtained from the Boulder Clay at Porth Colman : — 

 Several granite boulders from the Dalbeattie area ; a diorite very similar to that of 

 Col vend, Dalbeattie ; boulders of hornblende porphy rites, probably from the Dalbeattie 

 area, and chalk-flints. 



The following species were identified from amongst the shell-remains found in the 

 Boulder Clay at Porth Colman: — Turritella communis (Lam.), Astarte sulcata (Da 

 Costa), Cyprina islandica ( L.), Venus ( Ventricola) Casina (L.), Cardium echinatum (L.). 



Around Penrhyn Colman the coast is rocky, and at Porth-llefesig the rocky cliffs 

 reach heights of 50 to 60 feet. Above the rock lies a grassy slope of Drift. At the 

 northern end of the bay boulder gravel lies immediately above the rocky cliff, and this 

 is capped by stiff clay rather full of boulders and weathering yellow near the surface. 

 This clay contains some shell-fragments, but the only one which could be identified was 

 Astarte sulcata, 



