Horrid Mutiny and Massacre. — We are informed that Mr. Davis, first officer of the bark Isabella, just arrived at New-Bedford, brings a report that about twenty days prior to their departure from New Zealand, a shocking event occurred on board the ship Ploughboy, Capt. Brown, of this port — the particulars of which are thus related: In order to complete the crew of the ship, three natives of New Zealand were employed, who, having taken offence at the treatment received from some of the officers, revenged themselves by murdering two of the hands, and barbarously wounding a third. These atrocities were committed at night. The natives being forward, first beheaded a seaman who was on the watch; a boat-steerer, in the gangway, hearing a noise, and going forward to ascertain the cause, received a terrible cut from a hatchet, driven deeply into his shoulder; the man at the wheel was next attacked, pierced through the body with a spear, and fell dead through the skylight. Those below being thus aroused, hastened on deck, and found the murderers had cut adrift all the boats, in one of which they were endeavoring to escape. One of the natives was shot by those on the ship's deck, but the others got off. Next morning three of the boats were picked up, together with the dead body of the native. The name of one of the murdered seamen is stated to be John Coles, of Nantucket; the other was a native of Denmark, name not given — nor is that of the wounded man reported. — Nantucket Enq.