The author’s object in this paper is to describe the mechanism by which the boring and burrowing shell-fish form their habitations, and to explain some parts respecting the burrowing of other marine animals. After showing that the Nereides bury themselves by the undulating motion which they employ in swimming, aided by the action of their bristly feet, and that the Arenicola piscatorum forms its imperfect arenaceous tube by the aid of a viscid secretion which exudes from the anterior half of the animal, he particularly describes the habits of the Terebella conchilega, showing that by a glutinous secretion it cements together particles of shells and sand, so as to form a collar, which is regularly and curiously lengthened into a tube; and when this is about an inch in length the animal proceeds to burrow; and having completely concealed itself, is soon found to have turned within the tube. Mr. Osier describes the manner in which this motion is effected by reference to an annexed drawing.