My next four species are linked together by their avicularia, which in each case have the side walls infolded over a long deep-set area.

The Orthopteron wing which forms the subject of the present paper was obtained by Mr. David Davies from a dark-blue shale, about 10 feet in thickness, overlying the No. 2 Rhondda coal-seam in Clydach Vale (see Plate XV). The shale decreases to the east, dying out wholly 2 miles beyond the colliery, giving place to sandstone. I am indebted to Mr. Davies for the opportunity of describing the specimen.

Since the publication of Charles Darwin's memorable monograph on the Fossil Lepadidæ (Palæontographical Society, 1851) little has been written on the British Cretaceous Cirripedes. Among the thirteen species of Scalpellum which Darwin figured and described, ten are British, and, so far as I am aware, only one, Scalpellum attenuatum, has since been added to their number. Several species have, however, subsequently been described from Foreign Cretaceous Rocks.

The town of Dolgelley lies slightly outside the main tract of gold-bearing country of Merionethshire, but it forms a convenient headquarters from which to visit the various gold-mines and auriferous lodes. The Dolgelley Gold-belt lies within the area covered by the quarter-sheets 27 N.E., 27 S.E., 32 S.E., 33 N.W., 33 N.E., 33 S.W., 36 N.W., 36 N.E. of the 6 inch Ordnance Survey maps of Merionethshire. It is on the north side of the estuary of the Mawddach, extending from the sea at Barmouth to the locality of Gwynfynydd on the north-east. The belt forms the south-eastern flank of a range of high ground sloping down to the south and south-east from the mountains of Rhinog, Diphwys, and Garn. It is drained by several tributaries of the Mawddach, of which the principal are the Afons Hirgwm, Cwm-llechen, Cwm-mynach, Wnion, Las, Gamlan, Eden, and Gain.

Amongst the corals collected by the Geological Survey during the past season, and submitted to me for determination, two specimens call for special remark, since they appear at first sight to occur out of their true zonal position. They were found by Mr. Dixon on the Pembrokeshire coast, to the south and south-west of Castle Martin. In each case Mr. Dixon gives the horizon as C2–S1, in the terms of Dr. Vaughan's classification. They are, accordingly, of Lower Visean age.

The Liassic strata generally are so barren of any minerals of importance or of an appreciable size or extent that the record of the discovery of one not hitherto known to occur in a crystalline form, apart from the part it plays in the formation of shell-layers at that horizon, is assuredly of interest. Hitherto the Liassic strata have not yielded any minerals unassociated with shell-structure, except selenite, which occurs commonly in some Upper Liassic clays, whilst it is not unusual to find fossils converted into iron-pyrites or marcasite, especially at certain horizons. The Doggers of Yorkshire are noteworthy instances of this kind. In the Middle Lias, zinc, nickel, and cobalt are found in the iron-ores of the Cleveland district.