[Footnote 174: _Geol. Mag._ 1889, p. 22.] Llandovery. }Pentamerus grit. }Conglomerate (Mulloch Hill). Caradoc. {Shales, sandstones, grits, etc. (Ardmillan, Balcletchie). {Thick conglomerate (Byne Hill, Bennane, etc.). {Thick fossiliferous limestone (Stinchar, Girvan). (On this horizon { come the perlitic felsites and soda-felsites of Winkstone and Wrae.) {Sandstone (_Orthis confinis_) passing down into thick conglomerate. [Unconformability.] Upper Llandeilo. }Green mudstones, grits and greywackes. }Thin band of dark mudstone with Upper Llandeilo graptolites. Arenig and Lower and Middle Llandeilo. {Group of Radiolarian cherts (about 70 feet) with alternating tuffs. {Tuff or volcanic conglomerate, with occasional lava-flows. {Black shale (10 feet) with Arenig graptolites. {Volcanic breccias around local centres (Knockdolian, etc.). {Thick group of porphyrite and diabase lavas. {Red flinty mudstones with Arenig graptolites. {Porphyrites, etc. {Fine tuffs, etc., with Lower Arenig fossils. {Diabase lavas, etc. (base not seen). It will be noticed from this table that the bottom of the volcanic series is not reached, so that no estimate can be formed of its full thickness, nor on what geological platform it begins. Possibly its visible portions represent merely the closing scenes of a long volcanic history, which, over the area of the south of Scotland, extended into Cambrian time, like the contemporary series of Cader Idris.