seen on the E. side of the stream below Clegyr Bridge. These rocks have a thickness of about 400 feet ; and on the N.N.W. side of the axis the greenish flaggy sandstones also occur, resting conformably on the conglomerates.
On the S.S.E. side of the ridge the greenish flaggy sandstones have above them red shaly beds, agreeing in their inclination with the strata on which they repose ; and these red shaly beds have afforded the earliest traces of organic remains which have been hitherto discovered in the St. David's promontory. These remains consist of Lingula ferruginea, Salt., a form previously mentioned, another and larger Lingulella, a Distinct, and a new species of Leperditia of considerable size, L. cambrensis, Hicks.
These red shales occur on both sides of the quartziferous ridge. They are seen on the N.N.W. side, in Ramsay Sound, where fossils have also been obtained from them near Castell. A small fragment of a Trilobite has likewise been met with in the red shales of this locality ; but this fragment was not sufficiently distinct to allow of the form being satisfactorily determined.
On the S.S.E. side of the ridge the fossiliferous shales are seen at Porth Clais Harbour ; and in this spot also fossils occur*. They are likewise seen under the ruins of Nun's Chapel, at Rhoscarrylhuyd, and also at Caerfai and Mill. These red fossiliferous shales have a thickness of about 50 feet.
On the S.S.E. side of the axis, reposing conformably on the fossiliferous red shales, purple sandstones having occasional green bands associated in them occur, somewhat coarse in grain. These purple sandstones are about 1000 feet thick ; and hitherto no fossils have been obtained from them. These sandstones are now being largely worked, the stone used in the restoration of the Cathedral of St. David's being obtained from them. They afford large blocks, which dress well.
On the N.N.W. side of the axis the thick purple sandstones are represented by deposits having more varied colours. On the E. side of Ramsay Sound, where the fossiliferous red shales occur, these are seen to be succeeded by greenish sandstones, upon which are rocks reddish in colour passing upwards into a series of purple strata. Greenish sandstones rest upon the purple strata ; and above these are purple-coloured beds, having within them red layers. These varied-coloured sandstones represent the thick purple sandstones on the S.S.E. side of the axis ; and they are also almost unfossiliferous, so far as present observations go.
The thick purple sandstones of the S.S.E. side of the St. David's promontory have superposed conformably upon them yellowish- and grey-coloured sandstones and shales. In the lower portion of these yellow- coloured rocks there have been found remains of a large and new form of sponge, Protospongia major, Hicks. These strata, which have some conglomerate beds associated with them, have also afforded Trilobites, one of which appertains to a new genus, and the other forms are new species. These are Plutonia Sedgwickii,
- Davidson on the Earliest British Brachiopoda, Geol. Mag. vol. v. p. 306.
