The specimens on which the following notes are based were JL collected by Mr. H. T. Ferrar, M.A., F.G.S., while on a tour through New Zealand, during the time the “Discovery” was being overhauled in Lyttelton, on her return from the Antarctic. The topographical and field notes were also supplied by Mr. Ferrar, and it must be clearly understood that only the detailed petrographical descriptions are the work of the present writer.

The specimens were obtained near the middle of the North Island of New Zealand, and in the area marked “acidic volcanic rocks” in Sir James Hector's geological map of New Zealand, published in 1883. They all occur in the Taupo zone, the hot-lake district which lies roughly between Lake Taupo on the south and Lake Rotorua on the north.