I. General Geology. The North Head of Otago Harbour is situated in lat. 45° 47′ 30″ S. and in 170° 45′ long. E. It is 13 miles distant from the city of Dunedin, in a north-easterly direction. The head is a precipitous cliff facing nearly due east in its southern portion; but, bending slightly westwards in its northern portion, it runs from south 15° east to north 15° west, and therefore in this portion faces 15° to the north of east. The cliff has an altitude of 530 feet at its highest point almost in the middle of the section, and throughout its length it is more than 300 feet high, except at the southern end, where it slopes somewhat gradually to the sand-hills which skirt its base. The lower part of the southern end of the cliff is partly obscured by scree-slopes and blown sand, and for 200 yards from its northern extremity the lower part of the cliff is hidden beneath an immense slip. Elsewhere, for a length of a mile and a half, the cliff presents a surface that is almost perpendicular, and it thus affords a remarkably clear section nearly bare of vegetation and quite free from all those difficulties of interpretation that are always associated with folding and faulting. This cliff was briefly mentioned in a previous paper of mine, published in the Quarterly Journal of this Society in 1906 (vol. lxii, p. 417). In this description the general nature of the succession was indicated.