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ETHALIA ZELANDICA (Plate VI.).—Fig. 7 (late Rotella zelandica) is a well-polished, smooth shell, washed up in large numbers on the ocean beaches. The colours of the upper side vary, but are usually chestnut or purple waving lines on a yellowish-white ground. On the base is a circular band of purple round the columella, which is white. The interior is nacreous. Occasionally a shell is entirely pink, and then the circular band on the base is pink also. The largest shell I have seen was nearly one inch across, and, being very flat, would be only half an inch high. They appear to live in sandy ground, below low water mark in the ocean; and a dredge if drawn over one of their favourite spots will be filled with them. I have dredged half a bucketful at one cast between Karewa and Tauranga in five fathoms of water. The former name was Rotella zealandica, and Rotella, meaning a little wheel, well described the appearance of the shell, the waving line representing the spokes.
NATICA ZELANDICA (Plate VI.).—Fig. 8, a yellowish or reddish-brown shell, with chestnut-brown bands, the interior being pale brown, the mouth and its vicinity white. It is a clean, bright little shell, upwards of an inch across. Those in the ocean are lighter in colour, and larger and more solid than those found in harbours. As the tide falls in harbours, they conceal themselves near low water mark, especially in the vicinity of marine grass banks. When the tide is rising on a warm, sunny day they spring out of the sand, dropping sometimes two or three inches from where they had been concealed. The operculum is horny, with a shelly outer layer; and the animal is prettily mottled and striped red and white.
There are two other Natica found in New Zealand, neither of which exceeds one-third of an inch across, and in shape are very like the N. zelandica. The Natica australis is a brown or grey shell, and the Natica vitrea is white.
NERITA NIGRA (Plate VI.).—Fig. 9 (late Nerita saturata) is a heavy, solid blue-black shell, with a whitish interior. This sombre-looking member of a handsome tropical family (of which the bleeding tooth Nerita is the best known) is sometimes over an inch in length, and found in large numbers clinging to the surf-beaten rocks of the North Island, quite up to high water mark. The operculum is shelly and prettily mottled with purple. This shell will stand boiling water, and, in fact, boiling water is required to kill the animal, which is quite as tenacious of life as an oyster. The Maori name is Mata ngarahu.
