C. 3. Middle district-from Dulas on the North to Aberfraw on the South. C. 4. Small strip to the East of the last-between Red-wharf bay and Caint. C. 5. Western district-from Llandonna to Llandwyn. Serpentine. (S). S. 1. S. 2. In Holyhead Island-from Rhoscolyn to Llanfihangel. Greywacké. (G). G. 1. Between C. 1. and C. 2., and to the East of each as far as C. 3. G. 2. Towards the North of C. 3.-a small strip running from Bryngole to the S. W. G. 3. Bounds C. 3. on the S. E.-from the North of Llangefni, to the South of Aberfraw. G. 4. Between C. 4. and C. 5.- from Red-wharf bay to Llanfihangel East. G. 5. Small patch N.E. of the last-at Llandonna. G. 6. At the Eastern termination of C. 5.-West of Beaumaris. G. 7. To the South of the last.-At Garth-ferry, and on the opposite coast of Cærnarvonshire, from Bangor to Aber. Old Red Sandstone. (O). O. 1. Separates C. 1. and C. 3. at their Southern termination, and runs as far North as Llanerchymedd. O. 2. A small patch at the N. E. termination of the last-immediately South of Llanerchymedd. O. 3. A similar patch to the N.E. of Llanerchymedd. O. 4. Another, to the N. E. of the last-in contact with the Northern |