New Zealand — The following communication is from our Correspondent at the Bay of Islands: — "Arrived, July 7, the Black Warrior, from the coast; July 11, Harriett, Howe of Sydney, with 360 barrels of oil, crew down with scurvy; July 12, Cadmus, of America, 2200 barrels, thirty months out; Aquilla, Drysdale from Sydney, with sundries and sailed again July 17; July 18, Clarkstone, of America, 2900 barrels, thirty-six months out. This vessel reports the New Zealanders on board the American ship Ploughboy rising at night, and assassinating five of the crew — then making their escape in one of the boats. . . .