Such a succession can be found near the Waihao Forks. Here the green-sand strata that are exposed on the right bank of the river, between the Forks and McCulloch's bridge, are similar lithologically to the Hampden beds, and there is a clear stratigraphical succession to the local representative of the Oamaru limestone above, as has been clearly shown by McKay, Park, Marshall, and all others except Hutton, who gave a most surprising account of the stratigraphy. Not only are the Waihao greensands similar lithologically to the Hampden beds, but there is also a close palaeontological similarity, for the following fossils which have not yet been found in any higher or, indeed, any other strata occur in both of them—Polinices waihaoensis, Exilia waihaoensis, Turris regius, Turris complicatus, Surcula serotina, Fusinus solidus, and Euthriofusus spinosus—though up to the present time only very small collections have been made in the Waihao beds. The Hampden beds may therefore be considered as of much the same age as, though perhaps a little older than, those at Waihao. In this locality, however, the stratigraphy is not complicated by the occurrence of any strata of volcanic origin, and the greensands pass up without any break, and within a thickness of 100 ft. of strata, into a limestone which is thought by all observers except Park to be the local representative of the Oamaru limestone. No collection of fossils has yet been made from the limestone at the Waihao, but at Otiake, twenty miles distant, on the south side of the Waitaki River, there is a similar limestone, which is considered by all geologists who have examined this area to be of the same age, and in effect a continuation of the limestone stratum of the Waihao. At Otiake a collection of fossils was made by Marshall and others, who found sixty-one species, of which 24 per cent. were determined as Recent species.

The facts so far mentioned may be summarized as follows: At Coleridge Creek, in the Trelissick Basin, there is a fossiliferous horizon containing 19 per cent. of Recent species. This horizon is below the limestone (Speight, 1917, pp. 328 and 344), or 10 ft. below the upper surface of the Amuri limestone (Thomson, 1916, p. 51). In the greensands at Hampden there are 10 per cent. of Recent species. Lithologically and palaeonto-logically the Hampden beds are closely similar to those at the Waihao Forks, which pass up conformably into the arenaceous limestone. This limestone is always correlated with that at Otiake, which in its upper portion of 2 ft. or 3 ft. contains 24 per cent. of Recent species.

Such palaeontological evidence as we have at present therefore clearly points to the probability that the age of the Amuri limestone as developed in the Trelissick Basin is practically the same as the age of the Otiake limestone, which is admitted by all geologists except Park to be the same horizon as that of the Oamaru or Ototara limestone.

This consideration also shows that too much importance should not be attached to the absence of the Amuri limestone in Otago. This material is a Globigerina ooze, which was probably deposited on the floor of a deep, clear-water, oceanic area. The Oamaru or Ototara limestone was deposited in far shallower water, where Polyzoa abounded, but still outside the area to which sediment was carried. The Waihao and Otiake limestones, however, were deposited nearer to the shore, in an area to which terrigenous sediment was carried, and where tidal scour disturbed the sea-floor.

It seems unnecessary to call in the aid of local diastrophes to explain the differences between the Canterbury and Otago succession of Tertiary rocks, for, as I have often maintained, the differences that exist can easily be explained on general considerations. The Canterbury area was evidently

more deeply depressed during this middle Tertiary period than Otago, a fact that is clearly evidenced by the very nature of the Amuri limestone, which is often wholly composed of Globigerina, but in some cases of other pelagic organisms as well. In Otago, on the other hand, the limestones, whilst still free from all terrestrial sediment, consist mainly of organisms that live on the floor of moderately deep water only. While this is the case, however, it must still be remembered that at Oamaru the limestone rests on a deposit that is composed of diatoms, Radiolaria, and sponge-spicules. Park (1918, p. 50) has lately maintained that this is really a shallow-water deposit, an opinion that is based partly on the general geology of the district and partly on the nature of the mollusca and brachiopods that are found in the deposit. The fossil species to which he refers are not named. In a collection made by me in June, 1915, the following mollusca were obtained: Amusium zitteli (Hutton), Nuculana (Leda) sp., Lima sp. (small), and Terebratulina suessi (Zittel). These are all genera that have a wide occurrence in deep water, and until a list is published which contains the names of other mollusca, that have a shallow-water habitat there is no reason to suppose that the molluscan remains in these diatomaceous deposits are incompatible with the accumulation of the material on a deep oceanic floor. There is no reason to suppose that the water was of the same depth over all that portion of New Zealand that was then covered by the ocean. In Canterbury the area in which the Amuri limestone occurs was covered by deeper water than that portion of Otago where the Oamaru or Ototara limestone is found. It may therefore fairly be said that all the palaeontological evidence that is known at the present time supports the belief that the Oamaru limestone represents an horizon of the Amuri limestone, and that there are no stratigraphical or structural facts known that oppose this conclusion.

In the north of Auckland the so-called hydraulic limestone covers a large area. This limestone is also composed mainly of Globigerina ooze, and, like the Amuri limestone, it is often highly siliceous, and in places the siliceous organisms are calcified, though at others diatoms, Radiolaria, and sponge-spicules are in a perfectly fresh condition and can be obtained in large numbers. This limestone has generally been correlated with the Amuri limestone of Canterbury, and Thomson's objection to this has already been refuted (Marshall, 1919, p. 248, footnote). In addition, however, to the general stratigraphical position of this limestone, there is palaeontological evidence of considerable importance. At Pahi, on the Arapaoa arm of the Kaipara Harbour, there is on the foreshore a little to the west of Pahi Township a bed of greensand lying between two beds of the hydraulic limestone. This greensand contains a considerable number of fossils, as first noted by Park. The fossils, however, are in a bad state of preservation, and only a few of them can be identified specifically. The following were collected in 1916:—

• Atrina sp.

• Calliostoma sp.

• Cassidea n. sp.

• Corbula canaliculata (Hutt.)

• Cucullaea alta (Sow.)

• Cytherea sp.

• Dentalium solidum (Hutt.)

• Divaricella aff. cumingi (Ad. & Ang.)

• Limopsis zitteli (Iher.)

• Nucula sp.

• Nuculana aff. bellula (A. Ad.)

• Ostrea aff. corrugata (Hutt.)

• Panope worthingtoni (Hutt.)

• Polinices gibbosus (Hutt.)

• Psammobia sp.

• Struthiolaria sp.

• Surcula n. sp.

• Tellina sp.

• Turritella ambulacrum (Sow.)

• Venericardia aff. australis (Lamk.)