Extent.

In this group I include the melaphyres with their tufas and amygdaloids, the felsitic and quartziferous porphyries with their pitchstones and tufas of the East, and the melaphyres of the West Coasts. The first zone begins in this province on the southern declivities of Oxford Hill, where a small outlier of melaphyres and amygdaloids occurs. It then becomes largely developed in the southern portion of the Malvern Hills, and on both banks of the Rakaia, near the Upper Ferry. In this district, the melaphyres rise to an altitude of 2900 feet, and the quartziferous porphyries to 3019 feet (in High Peak).

Another small outlier of the latter is situated five miles from the beginning of the Canterbury plains, on the right bank of the northern Ashburton. On both banks of the southern Ashburton and Hinds rivers, both divisions of these eruptive rocks cover a large area, forming the summits of mountains of considerable dimensions, the basic rocks rising in the Clent Hills to 4100 feet, and the acidic rocks in Mount Somers to 5223 feet. The latter also crop up in one locality on the southern banks of the Orari. Another zone, possessing very interesting features, is found on Banks' Peninsula, consisting of quartziferous porphyry, pitchstones, and some tufaceous beds derived from them; whilst we meet, on the northern declivities of Mount Harper, with a small zone of melaphyre; on the right or southern banks of the Rangitata, between Forest and Coal Creeks, a large portion of the McLeod range consists of felsitic porphyry, amygdaloids and melaphyres, stretching across into the Upper Orari. In the more southern portions of the province, no eruptive rocks were observed by me in situ, but I found repeatedly boulders of similar porphyries in the lower Waihao, without however being able to discover the locality whence they became detached. I believe that the porphyries in the River Mandamus, north of the Hurunui, and in the Leslie Hills, north page 283of the Waiau river, described in my Report on the Geology of the Amuri district (Reports of Geological Explorations during 1870-71, Geological Survey of New Zealand) form the northern continuation of this zone. On the West Coast, only basic rocks appear to have been erupted, by which, south of Bruce Bay, a considerable portion of the coast line is now formed. I have already stated that they appear to be of a somewhat younger age than the eruptive rocks on the eastern side, because if the sedimentary beds, consisting of conglomerate, grits, shale, and coal, with which the melaphyres are associated, and which are doubtless of the same age as the Grey Coal Measures, are contemporaneous with the cretaceo-tertiary formation on the eastern side, which is very probable, they ought to be classed with the basic rocks, making their appearance during that period. However, my reason for placing them with the former is, that they possess all the characteristics of true melaphyres, having, moreover, extensive beds of tufas and amygdaloids associated with them.