half of the overfold and that the upper limb has subsequently been removed by erosion. Forward remmants of such a fold might in some cases show a structure somewhat similar to that of the feature described as the “Thrust.” The appearance of the monoclinal ridge of limestone in the Middle Clarence Valley, developed from the homoclinal series of beds east of the fault-plane, may thus be a falsely simple form derived from more complex conditions. If such be the case, then the mountains owe considerably more of their original height to folding than has been hitherto acknowledged, the final reversed faulting being responsible for only half the amount usually specified. To this hypothesis the rocks along the eastern base of the Seaward Kaikouras may be expected to yield significant data. The observations of McKay (in Hector, 1890, p. xxxv) are supported by Jobberns's investigations (1932, pp. 341–352) in the Puhi Puhi Valley, where he has demonstrated that the covering beds are involved in an overturned syncline between the Seaward Kaikouras and the Patutu or Coastal Range. * His diagrammatic section on p. 351 is an oversimplification by distortion of the true scale and his “fold lines” are not dislocated by the later faults. A much truer picture would probably be presented by incorporating some of the minor folding of Cotton's diagram which he reproduces on the opposite page. Jobberns's insistence upon folding rather than faulting is well illustrated in the following passage (loc. cit., p. 343): “Examination of these important sections (Puhi Puhi) leads to the conclusion that the area is a long synclinal depression, the syncline being overturned by thrusting pressure from the west. Faulting has, as might be expected, resulted from this thrusting, but it is of relatively a minor order, and its effect on the surface relief features has been overestimated.” A monoclinal ridge of limestone also exists east of the Patutu Range. In the neighbourhood of the Clarence River this ridge is of simple structure, but on the coast at Waipapa Point it appears to be folded into a close syncline. Here Speight (in Jobberns, 1932, p. 349) has observed that the Amuri Limestone is overridden by the sandstone of the Patutu Range so that in both folding and later fracturing the eastern base of the Patutu Range appears to be similar to both the Seaward and Inland Kaikouras. Structurally there is probably some connection by way of the Wharekiri Valley between Mount Alexander and the Limestone Range extending from Mole Hill to Jacob along the front of the Seaward Kaikouras in the Lower Clarence (see Fig. 6). The main branch, however, is offset and forms the ridge along the eastern base of Patutu Range. Thomson (1919, p. 301) records that the “Sawtooth Range is flanked on the south-eastern side by Clarentian rocks followed by the Amuri Limestone in the Lady Range.” Here steep faulting does not exist or is of relatively small amount, Sawtooth Range owing perhaps the greater part of its elevation to folding. The writer is not aware, however, whether this is so strong as to be termed an overfold. The axes of the folds appear to have been gently arched, a feature which has been noted by Thomson (1919, p. 321) along the Quail Flat Fault and deduced by him along the main Kaikoura