The sequence of strata on the Wanganui coast based on J. Park's survey (1887) is as follows, re-quoted from Thomson (1916, p. 36):—

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Thomson (1916) based two stage names upon this succession, viz., Castlecliffian for the Wanganui beds and Kai-iwi blue clays, and Waitotaran, based oupon Park's “Waitotara Coralline series.” The limit between these stages was purposely, and wisely, left vague.

Marshall and Murdoch (1920) published an excellent account of the faunal changes throughout the Wanganuian, but did not employ stage names.

In a table of classification of strata, prepared by P. G. Morgan (?) and published in a Bulletin by T. H. Withers (1924), it is stated that the Waitotaran “may be subdivided into Nukumaruian and Waipipian,” and a footnote adds: “Probably the term ‘Waitotaran’ as a stage name will drop out of use, and the more exact terms ‘Nukumaruian’ and ‘Waipipian,’ based upon Marshall and Murdoch's work (1920) will take its place.”

L. I. Grange (1926, p. 334, footnote) has pointed out that this is impossible since Thomson (1916) did not include the Nukumaru beds in his Waitotaran Stage. The Waipipian is the term which must drop out of use.

Marwick (1924 A) divided the Wanganuian into Waipipian, Nukumaruian, and Castlecliffian, but in a later paper (1924 B) Waitotaran was substituted for Waipipian. The same author (1926 A, p. 267) later separated off the Kai-iwi beds because “a preliminary survey indicates that a useful stage may be recognisable between the Nukumaruian and Castlecliffian.” Thomson (1916), however, included the Kai-iwi beds in the Castlecliffian. Marwick's latest scheme (1927) distributed the stratigraphical units as follows:—

These various stage names, therefore, have been employed rather loosely, and should be redefined. It is generally admitted that three stages are represented in the sequence, and for these the terms Castlecliffian, Nukumaruian, and Waitotaran have found general acceptance. It is probable that future research will prove that each of these stages contains more than one faunal community. The exact range of these communities is not yet accurately known. However, the writer believes that it would be wise to define the three stages with reference to certain definite stratigraphical units. The minor faunal communities, when their range is established, can form the basis of zones within the major scheme here outlined.

The Castlecliffian may be defined as the interval of time represented by the deposition of the Wanganui, Kai-iwi, and Okehu beds of Park (1887), and as well such periods as may be represented therein by non-deposition or erosion^*.

Henderson (1929) has noted that the lowest beds of the Castlecliffian contain much pumice, and a seam of lignite. He believes that the Castlecliffian strata result from a minor sea transgression which followed uplift at the end of the Nukumaruian period. If this is so the Nukumaruian-Castlecliffian junction may conceal a considerable time interval.

The characteristic mollusca of the Castlecliffian based upon collections made by the writer, and further material in the Finlay collection, and determined by Dr. Finlay, are^†:—Acteon ambiguus (Hutt.), (= sulcata Hutt.), Aeneator marshalli (Murdoch), Alcithoe gracilis (Swainson), A. swainsoni Marwick, Alocospira novaezelandiae (Sow.), Amphidesma pliocenica Oliver, Antisolarium egenum (Gould), Arthritica bifurca (Webster), Astrea heliotropium (Martyn), Ataxocerithium huttoni (Cossm.), Austrodrillia wanganuiensis (Hutt.), Austrofusus glans (Bolten), Barbatia novaezelandiae Smith, Baryspira (Pinguispira) lata (Hutton), B. mucronata (Sow.), Cardita aoteana Finlay, Chlamys radiatus (Hutton), Cochlis australis (Hutt.), C. zelandica (Q. & G.), Coelotrochus huttoni (Cossm.), Coluzea spiralis (A. Ad.), Corbula macilenta Hutt., Cosa wanganuica Finlay, Divaricella cumingi Ad. and Ang., Dosinia (Phacosoma) wanganuiensis Marwick, Dosinula zelandica (Gray), “Drillia” buchanani (Hutt.), Estea impressa (Hutt.), E. semisulcata (Hutt.), Eucominia elegantula Finlay, Evarnula striata (Hutt.), Gari lineolata (Gray), Glaphyrina progenitor Finlay, Glycymeris laticostata (Q. & G.), Iredalula striata (Hutt.), Mantellum marwicki Powell, Maoricolpus roseus (Q. & G.), Maoricrypta costata (Sow.), Maurea hodgei (Hutt.), Melliteryx parva (Deshayes), Murexsul octogonus (Q. & G.), Myadora striata (Q. & G.), Nemocardium pulchellum (Gray), Notocallista multistriata (Sow.), Notolepton antipodum (Filhol), Nuculana bellula (A. Ad.), Ostrea sinuata Lam.,

Pachykellya edwardsi Bernard, Panope zelandica Q. & G., Paphirus largillierti (Philippi), Pelicaria vermis (Martyn), Phenatoma novae-zelandiae (Reeve), Pleuromeris zelandica (Deshayes), Poirieria zelandica (Q. & G.), Pteronotus zelandicus (Hutt.), Saxicava australis Lam., Scalpomactra scalpellum (Reeve), Semicassis multisecta (Finlay), Sigapatella inflata (Hutt.), Splendrillia laevis (Hutt.), Stirocolpus symmetricus (Hutt.), Struthiolaria papulosa (Martyn), Tawera wanganuiensis Marwick, Tellina eugonia Suter, T. urinatoria Suter, Tugali pliocenica Finlay, Venericardia purpurata (Desh.), Verconella mandarina (Duclos), Xymene plebeja (Hutt.), Zeacolpus vittatus (Hutt.), Zeatropon ambiguus (Phil.), Z. bonneti (Cossm.), Zemitrella sulcata (Hutt.), Zemysia zelandica (Gray), Zenatia acinaces Q. & G., and Zethalia zelandica (A. Adams).

The Nukumaruian may be defined as the interval of time represented by the deposition of the Nukumaru beds as exposed on the Wanganui coast, and as well such periods as are represented therein by non-deposition or erosion.

The characteristic mollusca of the Nukumaruian Stage, based upon personal collections from the type locality, Nukumaru, and determined by Dr. Finlay, are:—Alcithoe detrita Marwick, A. nukumaruensis (M. & M.), Anomia undata Hutton, Austrovenus crassitesta Finlay, Baryspira (Pinguispira) lata Hutt., B. (P.) opima Marwick, M. mucronata (Sow.), Bassina yatei (Gray), Cominista obsoleta Finlay, Corbula macilenta Hutt., Cosa trigonopsis (Hutt.), Dosinia (Raina) nukumaruensis Marwick, Dosinula zealandica (Gray), Estea semisulcata (Hutton), Eucominia exoriata Finlay, Isognomon zelandicum (Suter), Lutraria solida Hutt., Maorimactra acuminella Finlay, Ostrea sinuata Lam., O. (Crassostrea) ingens Zittel, Pallium mariae Finlay, Pervicacia tristris (Deshayes), Pleuromeris zelandica (Desh.), Pteromyrtea dispar (Hutt.), Tawera subsulcata (Suter), Venericardia purpurata (Desh.), Verconella allani Finlay, Xymene drewi (Hutt.) and Zethalia zelandica (A. Adams).

The Waitotaran^* may be defined as the interval of time represented by the deposition of the pre-Nukumaruian strata exposed on the Wanganui coast, and as well such periods as are represented therein by non-deposition or erosion.

An incomplete list of the characteristic mollusca is as follows:—Alcithoe gatesi Marwick, Cardium spatiosum (Hutt.), Cochlis haweraensis (Marwick), Dosinia (Raina) waipipiensis Marwick, Eumarcia plana Marwick, Fissidentalium solidum (Hutt.), Glycymeris manaiaensis Marwick, Lima waipipiensis (M. & M.), Miltha neozelanica M. & M., Olivella neozelanica (Hutt.), Ostrea (Crassostrea) ingens Zittel, Pallium mariae Finlay, Pelicaria zelandiae (M. & M.), Phialopecten triphooki (Zittel), Polinices ovuloides (Marwick), P. waipipiensis (Marwick) and Tawera errans Marwick.

The stages of the Wanganuian are somewhat loosely defined. The writer believes that further research on this classic coast line