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(c) Miocene.
Miogypsina appears for the first time, and is abundant in, and limited to, the Hutchinsonian. This also applies to our various species of Lepidocyclina, which are all Nephrolepidine. Crespin (1936, p. 11) has noted that all the Victorian Lepidocyclines are also Nephrolepidine, and that in the Dutch East Indies and New Guinea these have their greatest development in the early part of stage “f,” which is equivalent to the Middle Miocene, a few of the species ranging up from the Lower Miocene stage “e.”
Some interesting faunal connections can be traced through these orbitoid forms, as follows:—Pakaurangi Point has a well-known and truly Hutchinsonian Molluscan fauna (Laws, 1939, p. 466) and an
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abundance of the Upper Aquitanian–Lower Helvetian Miogypsina irregularis Mich.; its micro-fauna is almost duplicated at a Poverty Bay locality, which also contains Nephrolepidina tournouri L. and D., marginata Mich., borneensis Provale and sumatrensis Brady (with var. mirabilis Y. and H.), together with Amphistegina lessoni d'Orb. and Gypsina howchini Chap. Equivalent horizons in the Waitemata beds of Auckland, the basal Mahoenui of Taranaki, and the lower “Blue Bottom” of the South Island West Coast contain Carpenteria rotaliformis Chapman and Crespin, Calcarina mackayi (Karrer) and Nephrolepidina orakeiensis (Karrer) (probably a synonym of martini Schlumb.). This horizon certainly corresponds with those from the Australian Janjukian containing these same orbitoids and referred to high in the Lower Miocene between stages “e” and “f,” by Crespin (l.c., p. 12). Below it, in New Zealand, but still placed in the Lower Miocene, is the Lower Hutchinsonian, discussed later.
The correlation of the Hutchinsonian as a whole with the Janjukian-Balcombian is confirmed by many other species. Because of the few Australian faunas seen, however, and their considerable specific difference and distinctive facies from ours, it is not yet possible to say which divisions of about Lower Miocene age more nearly correspond across the Tasman. The restricted genus Victoriella Chap. and Cresp., hitherto known only from the Oligocene of Hungary and the Lower Miocene of Australia, has been found in the Caversham sandstone at Burnside as a new species close to plecte (Chap.). The index New Zealand species Calcarina mackayi (Karrer) (see Finlay, 1939A, p. 527) is known only from our “true” Hutchinsonian (for remarks on this and possibly “false” or Lower Hutchinsonian, see later in this paper), and is common in the Janjukian, but replaced by a distinct form (verriculata Howchin and Parr) in the slightly higher Balcombian—both formations being referred to the Lower Miocene by Singleton (1935, p. 130; 1937, p. 442). Pavonia triformis Parr (1933, p. 29) is a rare and distinctive form previously confined to the Janjukian and Balcombian and the Miocene of Java; it is not uncommon in the true Hutchinsonian of Pakaurangi Point, but absent elsewhere in New Zealand. Planorbulinella plana (H.–A. and E.) is known only from these Australian horizons and the true Hutchinsonian of Nelson (Takaka), Westland (Marsden), and Taranaki (Mahoenui). Cerobertina Finlay (1939B, p. 118) ranges from Mid-Eocene to Recent in New Zealand, but only the true Hutchinsonian bartrumi compares with the Australian forms seen; it is very close to the Janjukian-Balcombian dehiscens H.-A. and E. The allied Ceratocancris Finlay (1939B, p. 117) has a restricted true Hutchinsonian range and appears to be recorded only from the Australian Balcombian; a very closely allied species is in the Vienna Miocene. The index genus of the Australian Balcombian, Hofkerina Chapman and Parr (1931, p. 237), is known in New Zealand only from the true Hutchinsonian of Pakaurangi Point by a species apparently identical with semiornata, the genotype. It would take too long to detail completely the many other described Janjukian and Balcombian
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species that occur, or have allies, in our Hutchinsonian—the micro-faunal affinity between these stages is stronger than any other trans-Tasman link in the Tertiary. Allan (1940, p. 280) has recently written that “it is probable that the Hutchinsonian stage … is older than the Janjukian beds,” but gives no evidence or reference to others' opinions to support this assumption.
Chapman (1932B) made the important discovery of Miogypsinoides Y. and H. in New Zealand, in slides sent him by Speight from the Mount Somers district. M. nitidula Chap. was found at three localities (Chapman Creek, Bland's, and Stavely limestone); from the first two Marwick and Allan (in Speight, 1938, pp. 61, 62) have recorded Lower Hutchinsonian brachiopods and molluscs, and Allan (l.c., p. 91) has given a Hutchinsonian age for the latter, so that the horizon here of Miogypsinoides seems to be entirely Lower Hutchinsonian. Chapman's supposition that it came partly from (and proved the Lower Miocene age of) the Ototaran is erroneous. The importance of these records lies in the fact that the genus is known elsewhere only in the top of the Dutch East Indies stage “e” and base of “f”—Aquitanian and basal Burdigalian. This corresponds excellently with the Lower Miocene age Finlay allotted to the Hutchinsonian (its lower part would then be basal Miocene), with the Duntroonian-Waitakian Aquitanian.
A few links are known with faunas still further afield. Some matrix examined from the Burdigalian of France contains a species of Virgulopsis Finlay very close to the index species pustulata Finlay, limited to the New Zealand true Hutchinsonian and Awamoan. Hopkinsina notohispida Finlay (not below Awamoan) and Siphogenerina ongleyi Finlay (not below Whaingaroan) both seem to occur in the Miocene of French Morocco (Lacoste and Rey, 1938, chart, opp. p. 320 and Pl. 21) not below the Burdigalian. Operculina, so useful in Australia and America, is known here only from a distinct species at one locality, referred to Lower Miocene by Chapman and Parr (1938, p. 288), but probably older; of all the Austral and Indo-Pacific species they discuss it is the closest related to the French complanata Defr., known from Aquitanian to Lower Burdigalian in Europe and French Morocco (Lacoste and Rey, 1938, l.c.).
A rich fauna has been examined from the base of the Ouba series of New Guinea (basal “g” stage, regarded as Upper Miocene); a surprising similarity to our Taranakian is evident, almost all our Upper Miocene key-species being represented by close allies. Another fauna from the Upper Mena series (upper “f” stage—Middle Miocene) is even closer in a most striking fashion, to our Tutamoe (Awamoan) especially as developed in Hawke's Bay.
On the other hand extremely little relationship exists between figured faunas of the American Miocene and any New Zealand fauna placed here within the range Lower Oligocene-Pliocene.