The Island of Grand Manan, the natural history of which this paper is intended to illustrate, is perhaps but little known, geographically, to many who may be readers of this account. It may not be out of place, therefore, to make some remarks on its position. It is more properly an archipelago than an island. The smaller members of the group lie to the east of the largest, which is twenty miles in length, with a general trend north-east and south-west, having an average breadth of nine or ten miles. It lies at the mouth of the Bay of Fundy, about ten miles from the western shore at Campo-bello and Eastport, and thirty from the Nova Scotia shore. It is surrounded on all sides by deep water (a hundred fathoms or more), as might be judged from the character of the shores, which are rocky and precipitous, especially on the western side, where cliffs of a basaltic structure rise perpendicularly to a height of several hundred feet. On the south-eastern side, where there are numerous islands, the shores are low and shelving, composed of Mica-slate having a dip of about The passages between these islands, worn out by the tides which rush with great velocity through them, are generally very shallow, while a short distance seaward the water becomes as deep as on the western side. The following paper is intended as a compend of observations made on the marine fauna of this region, during three months' residence in the summer of 1852; and also as a catalogue, which it is hoped will prove nearly complete, of the marine invertebrates found on its shores and in the adjacent waters.