In the typical fauna at Mt. Brown occur Magadina and the restricted Waiparia intermedia-abnormis; the latter species-group is here used to correlate with this the Waiparia zone at All Day Bay, the Waiparia-bearing Caversham sandstone of Dunedin district (Thomson, 1918, p. 197), and the Middle Ihungia brachiopod horizon of Poverty Bay (again with Waiparia abundant, but no Pachymagas). From the three last-named, good foram faunas have been obtained, but the molluscan fauna comes chiefly from the beds above the limestone at Clifden, the Pakaurangi Point beds, the Mahoenui and Ihungia mudstones (deeper water), and the Waitemata Oneroa beds (shallow water, with Magadina) (Powell and Bartrum, 1929, p. 395). Forams also allow correlation with the Lower “Blue Bottom” of Marsden and other localities in Westland, where there are no molluscs or brachiopods. Although the molluscan beds at Clifden lie above the parki limestone, faunal comparisons between them (up to as far as the “Stethothyris zone”), and the Middle and Upper Ihungia and Pakaurangi Point beds indicate that they still fall within the Hutchinsonian. When the Tertiary as a whole is considered, a separate division of stage value does not appear to us to be warranted for these beds. Finlay (1939A, p. 530) mentioned that a small new stage might be needed here, but much additional information from micro-faunas, accumulated since, negatives the idea. Allan (1940, p. 289) has again suggested that this horizon merits a stage name, but no definite correlation can be made with it elsewhere, and it would have to be postulated as missing or unrecognisable in all other, apparently normal, sections. Such theoretical “stages,” based on rather thin deposits in the South Island, do not merit serious consideration unless they can be usefully employed in connection with much thicker and more continuous beds in the North Island. For a number of cogent reasons, no new stage name is here proposed for Lower Hutchinsonian as distinct from the True Hutchinsonian, but for convenience the faunal analyses are presented separately. The term “True” is used rather than “Upper” Hutchinsonian to avoid confusion with Park's usage of the latter. (a) Key fauna of Lower Hutchinsonian. Restricted forms:— (M) None known as yet, the molluscs of this horizon being either very poorly preserved or but little collected. (B) Pachymagas haasti Th., marshalli Th. (and similar large forms with primitive folding and cardinalia), Rhizothyris simple species (rare till true Hutchinsonian). Tegulorhynchia antipoda Th. and aff. coelospina C. and C., Campages neozelanica Allan. (Corals) Isis dactyla T.-W., Mopsea hamiltoni Th. (Isis has been found in the basal Ihungia—see Marwick, 1931B, p. 38.) (F) Haeuslerella hectori, Victoriella aff. plecte (Chap.). First appearance of:— (M) None known as yet.