ON THE OLDER KOCKS OF ANGLESEY. 415 



leaving evident traces in their structure, does not prevent our recognising 

 in them a vast and varied complex to which perhaps there is no parallel 

 in the later rocks of Britain. 



List of the Rocks eefebeed to in the foregoing Report. 



1. Great Quarry, Holyhead— Quartzite with foliation cleavage (fig. 12). 



2. Porth-jTT-Ogof, Holyhead — Quartzite with coarse groundmass. 



3. Central series, Holyhead — Impure quartzite. 



4. Porth-yr-Ogof, Holyhead, at junction— Impure quartzite with mica frag- 



ments. 



5. Porth-y-felin, Holyhead — Laminated with parallel foliation (fig. 3). 



6. Porth-yr-Corwgl, Holyhead— Showing solution of broken quartz (fig. 13). 



7. East side of Straits, near Valley — Fine-grained rock. 



8. Near Chapel, Four Mile Bridge — Fine laminated schist. 



9. Caer Ceiliog,near Valley— Fine-grained rock, with mica orientated obliquely 



to a strain-slip cleavage. 



10. Crossing of Paver Alaw — Coarse fragmental rock. 



11. Peniel — Green dust rock. 



12. Porth Dryw — Fine mylonitic slate. 



13. Beyond Porth Dryw — Mylonised in direction of bedding, with large frag- 



ments. 



14. South point of Porth Delise — Serpentinous mineral in tufts. 



15. South point of Porth Delise — Irregular calcite with large mica. 



16. Infusion south of Porth Defaid — Infusion of calcite and quartz with chalco- 



pyrite. 



17. South of Porth Defaid — Laminated schist. 



18. Green, East of Llanfachreth — Fine-grained rock. 



19. Abersant, Llantrissant — mica-schist with elemental orientation — zircons. 



20. Llanddeussant — Fine-grained rock with mica orientated obliquely to a 



strain-sUp cleavage (fig. 10). 



21. North of River Alaw — Coarse fragmental rock, fragments mostly felspar. 



22. Llanbaban — Mosaic rock with tension areas. 



23. East of Bodedern — Fine-grained rock with abundant orientated green mica. 



24. By Caer-deon, Llanddeussant — Fine-grained rock with tension areas 



25. Pont-scypbydd, north of Llanddeussant — Fine-grained rock, mylonised in the 



direction of the bedding. 



26. Llanfaethlu limestone — Fine mosaic limestone. 



27. Associate of Llanfaethlu limestone — Fine mosaic rock. 



28. Church Bay — Fine-grained rock with large fragments. 



29. Church Bay— Fine tuff. 



30. Llanrhyddlad — Fine mosaic rock. 



31. Summit over Ogo Lowry — Fine-grained rock with many quartzose frao'- 



ments. 



32. Hill over Ogo Lowry — Mosaic rock or marbled slate (fig. 4). 



33. Pant-yr-Eglwys — Granular felsite. 



34. Pant-yr-Eglwys — Dust rock. 



35. Near Pant-3-r-Eglwys — Felsite. 



36. Quartz knob, Pen-bryn-yr-Eglwys — Quartz elements with sericitic boundaries, 



37. Pen-brjTi-yr-Eglwys — Granular felsite. 



38. Pen-bryn-yr-Eglwys — Plagioclase and chlorite. 



39. Near summit, Pen-bryn-yr-Eglwys — Chloritised (epi ?) diorite. 



40. Pen-bryn-yr-Eglwys, north side— Granite with minute hematites, 



41. Pen-bryn-jT-Eglwys, north side — Cataclastic granite. 



42. Bottom of Pen-bryn-yr-Eglwys, by fault — Powdered granite. 



43. Monachtj', junction of granite and ash, Brecciated granite. 



44. Behind Monachty — Aplite. 



45. Ty Newydd, Valley — Enstatite gabbro. 



46. Dinas Fawr, Four Mile Bridge— Gabbro with eyes of diallage. 



47. Dinas Fawr, Four Mile Bridge— Mylonised gabbro with relics of diallage. 



48. Yr Hendty, Four Mile Bridge — Talcose epidote schist. 



49. Penryn Fadoc, Four Mile Bridge — Jlylonised talcose epidote schist. 



