From Rochefort’s 1666 The History of the Caribby-Islands (p. 107):
A particular Description of the Sea-Unicorn which was cast ashore at the Haven of the Tortoise-Island, in the Year 1644. and a pleasant Relation, by way of Digression, of several beautiful and rare Horns brought lately from Davis-streight; with an account of the Country, and the Dispositions of the Inhabitants.
We cannot better conclude the Account we had to give of the Sea-monsters, then with a description of so remarkable and miraculous a Fish, as may justly deserve a particular Chapter to treat of it: It is the Sea-Uni|corn, which is sometimes seen in those parts. There was cast ashore, in the year 1644. a prodigious one, on the Coast of the Tortoise-Island, neer Hispaniola.
Available on EEBO.