9-12-74. Aberisdy Bay. Type section of Hlanwin N.side of St. David's some miles north is location of Hlanwin type section Llanduvin Farm - is type section; there is no town of Hlanduin loc. 3. Classic muschisoni locality loc.4. These 2 bes. Covered by water - tide in + up. Origin of rocks for Stonehenge. Priesilli Hills. Works done by amateur gelogist at S.T.C. Blue-grey volcanic rocks carried by softs down streams to Bristol Channel to Avon then over Mendip Hills, Cotwolds & - these were open chalk areas to Salisbury Plains.