But about the Imperial Trochus, with its “orbicularly conical” shell—that term we may explain as round and cone-like; a reference to Fig. 4, Plate IV, will shew what is meant by this more clearly than words can, and likewise exhibit the beautiful markings of this species, with its ground tint of rich violet brown. This beauty is often obscured by calcarious incrustations, and marine plants, shewing that the mollusk is sluggish in its habits—a slothful creature. So it is with human beings, sloth covers and hides the good qualities and virtues with an overgrowth at all times difficult to remove, and oftentimes destructive of all that is fair and good in the character.—Children, be not slothful! The Obelisk Trochus, (_T. obeliscus_,) is a rare white and green shell, sometimes seen in collections; it is of a conico-pyramidal form, not remarkable for beauty, and is a native of the Indian seas. Mr. Gosse speaks of the Tops and Winkles as among the most useful inhabitants of the Aquarium; they mow down with their rasping tongues the thick growth of _Confervæ_ which would otherwise spread like a green curtain over the glass walls of the tank, and obstruct the view of its inhabitants. Here is this author’s description of the beautiful piece of mechanism by which this work is effected:—“The appearance and position of the organ would surprise any one who searched for it for the first time, and as it is easily found, and as Periwinkles are no rarities, let me commend it to your examination. The easiest mode of extracting it, supposing you are looking for _it_ alone, is to slit the thick muzzle between the two tentacles, when the point of a needle will catch and draw out what looks like a slender white thread, two inches or more in length, one end of which is attached to the throat, and the other, which is free, you will see coiled in a beautiful spiral manner, within the cavity of the stomach. By allowing this tiny thread to stretch itself on a plate of glass, which is easily done by putting a drop of water on it first, which may then be drained off and dried, you will find that it is in reality an excessively delicate ribbon, of transparent cartilaginous substance or membrane, on which are set spinous teeth of glassy texture and brilliancy. They are perfectly regular, and arranged in three rows, of which the middle ones are three-pointed, while on each of the outer rows a three-pointed tooth alternates with a larger curved one, somewhat boat-like in form. All the teeth project from the surface of the tongue on hooked curves, and all point in the same direction.”