Of special interest in the reconstruction of the past is the evidence afforded by our quite considerable fauna of native land snails particularly two genera, Paryphanta and Placostylus. Paryphantid snails have large, flatly coiled shells ranging from 2–3 ½ in. in diameter. The animal is carnivorous, feeding on earthworms and living in damp leaf mould on the forest floor, mostly at high altitudes. These snails belong to an ancient and primitive southern family that now ranges from South Africa to Melanesia. Their main distribution was probably achieved during the early Tertiary or even Cretaceous times. New Zealand has the largest number of species of this interesting group, and they could very well have originated in this part of the world. The fact that these snails produce large shelled eggs, resembling those of birds, and that these eggs will not survive dryness or immersion in water makes the distributional patterns of the Paryphanta species of special significance in the reconstruction of former geographical features and past land connections.

Similarly, the other genus of large New Zealand snails, Placostylus, is of equal significance in the reconstruction of the past. Placostylus snails are vegetarian, feeding on the dead leaves off coastal trees, mostly karaka. They grow up to 3 in. or more in length, and in shape are narrow and tall spired. They have been found in New Zealand only in Northland and outlying islands, never far from the sea and on the East Coast, not below Whangarei.

The special significance of Placostylus is that the genus is known elsewhere only from the islands of Melanesia, and northwards to the Solomons and eastwards as far as Fiji. This indicates some connection between New Zealand and the Melanesian area within comparatively recent times. This does not necessarily mean continuous land at any one time, but rather it suggests a series of give and take connections between island groups, and the gradual emergence of the present distributional pattern. The distribution of the kauri tree (Agathis) and of another plant (Xeronema), known only from New Caledonia and on islands of the Northland coast, lends support to this connection.

by Arthur William Baden Powell, Assistant Director, Auckland Institute and Museum.

• Shells of New Zealand, Powell, A. W. B. (1957)
• Transactions of the Royal Society of New Zealand, Vol. 66 (1937), “Animal Communities of the Sea-bottom in Auckland and Manukau Harbours”, Powell, A. W. B.
• ibid., Vol. 54 (1923), “Marine Littoral Plant and Animal Communities in New Zealand”, Oliver, W. R. B.;
• New Zealand Journal of Science and Technology (B) Vol. 33 (1951), “Some Animal Communities of the Sea Bottom from Queen Charlotte Sound, New Zealand”, Dell, R. K.