THE GLACIAL DEPOSITS OF WESTERN CARNARVONSHIRE. 



31 



of the crystals measured 2^ inches in length. Several pebbles of the Ailsa Craig rock 

 were also picked up on the beach. 



Length of section about 450 feet. 



a — a. Boulder gravel bed. 



b. Laminated clay. 



c. Tough boulder clay weathering into pinnacles. 



Fig. 3. — Diagrammatic Section of the Cliff East of Aberdaron. 



Among the included stones picked out of the Boulder Clay were chalk-flints, the 

 Ailsa Craig micro-granite, granite from the Dalbeattie area, the Goat-Fell granite of 

 Arran, and the Loch Dee granite of the south-west of Scotland. In addition to these 



Boulder clay 

 pebbly in places. 



Boulder clay. 



60 feet. 



' 40 feet. 



Fig. 4. — Section (diagrammatic) East End of Aberdaron Bay. 



there were boulders of Carboniferous Limestone, probably from Anglesey, of a reddish- 

 streaked rhyolite, of jasper, and serpentine. 



Amongst the shell-fragments obtained the following have been recognised : — 



Gasteropoda. 



Turritella communis, Lam. 

 Buccinum undatum, L. 

 Trophon (Boreotrophon) clathratus, L. 

 Bela turricula. 



Lambllibbanchia. 



Pectunculus glycimeris, L. 

 Mytilus edulis, L. 

 Astarte sulcata, Da Costa. 

 Astarte (Nicania) compressa, Mont. 

 Cyprina islandica, L. 

 Tellina (Macoma) balthica, L. 

 Cardium echinatum, L. 

 Cardium edule, L. 

 My a truncata, L. 



A portion of a Belemnite was also found in the Boulder Clay. 



Forth Cadlan ( Ysgo). — The Lower Boulder Clay is not exposed in this bay. About 



