of schist or quartz, the last gradually becoming more abundant towards the upper part of the series which, apart from the coal-seams and associated shale, consists almost wholly of well-rounded quartz pebbles and sand. This seems to form into limonite-stained sandstone about 80 ft. thick containing rare marine mollusca, the Herbert series of Brown (1938), who notes the difficulty of mapping it as a unit separate from the coal-measures in which it is here included. In the Pleasant Valley area south-west of Shag Valley, the coal-measures rest on Maniototo Schist and are, at most, 150 ft. thick. West of Smyler's Peak, the basal portion is a cemented quartz-conglomerate containing rarely fragments of schist. Elsewhere it is chiefly quartz-sandstone with pebbly bands identical in character with the higher beds at Shag Point. The highest portion is of finer grain-size and is possibly the equivalent of the molluscan beds, as Brown (1938) suggests, though no fossils have been seen in it. Plant-impressions and impersistent layers of valueless coal occur in the shales in the basal beds of the Horse Range. The more persistent and valuable seams are near the top of the series in the quartz-conglomerate and sandstones beneath the limonitic sandstone. Haast (1877) noted 9 or 10 thin (3–12 ins.) seams in Terapupu Creek, two (one 3 ft. 9 in. thick) on the flanks of Pukeiwitai, and 8 (including one 6 ft. 6 in. thick) in Mount Vulcan, where Macdonald (1912) noted 11 seams more than a foot thick when the field was being actively exploited. At present two small mines near Shag Point are working seams respectively 6 ft. and 3 ft. 6 in. thick, the latter occurring in the sandstone immediately below the molluscan beds. No coal has been found in the Pleasant Valley area herein mapped, though it was noted in the adjacent portion of the Goodwood District (Haast, 1877; Hector, 1892; Service, 1934). Opinions have varied as to the mutual relations of the formations here grouped together as the Coal-measures. Haast (1877) thought that two unconformable formations were present within the Horse Range series as here considered, and correlated the younger of these with the coal-measures in Pleasant Valley. Others have seen no unconformity within the Horse Range beds. Hutton (1875), Park (1903, 1910, 1911, 1912), and Macdonald (1912) thought a general unconformity occurred immediately above the Katiki Beach beds coeval with that below the Pleasant Valley coal-measures. Cox (1883), McKay (1887a), Hector (1886), and Marshall (1912) thought that the coal-measures on either side of the Shag Valley were members of a single sedimentary series. In the writer's view the lower portion of the Horse Range conglomerates were accumulated in a depression during or immediately after its formation by faulting and down-warping on the north-eastern side of the fault-zone, and therefore material derived from the weathering of the Maniototo Schist as well as larger fragmental blocks of semi-talus origin derived from the semi-schist, were incorporated in these conglomerates. When the depression was filled, these deposits were covered conformably by quartz-conglomerates and sandstones which overlapped beyond it to lie directly on the schist on the south side of the Shag Valley. From here similar siliceous beds lying on schist have been traced almost continuously southwards into the Dunedin district, where they