Of all the gastropods none excel the curious Xenophora in point of oddity. The shell is in general form like that of the top shell, but as it grows it attaches to itself small stones and pieces of shell, so that when the animal is fully grown it looks like a heap of dead shells and pebbles. This habit is in all probability to conceal the animal from its enemies. They are called “carriers” and the individuals with shells attached to their house are called Conchologists, while those with stones attached are called Mineralogists. The fragments of shells are attached with concave sides upward so as not to impede the animal during locomotion. The carriers are not able to glide like other mollusks, their feet being very small. They progress by lifting the front part of the foot to an object and then drawing the hind part toward it. In this way they jump or scramble along in a ludicrous manner. Related to the “carriers” are the slipper-shells (Crepidula), the horse-hoof shell (Hipponyx) and the bonnet-limpet (Capulus). The slipper shells are found in many parts of the world and are particularly abundant on the Atlantic and Pacific shores of the United States. The shell is flat and somewhat limpet-like, and across one end, near the apex, is a little shelf which gives it the appearance of a Chinese slipper. They adhere to stones, shells, crabs and any submerged object, and modify the form of their shell to fit the inequalities of their resting place. Thus a Crepidula on a Pecten shell will be ribbed while the same species on a stone will be perfectly smooth. Frequently they may be seen piled one upon another in tiers of six or more. The animal generally feeds on seaweed but has been known to eat other mollusks. The bonnet limpets also belong to this family, as do the cup-and-saucer limpets (Calyptraea). The family Strombidae contains many large and interesting shells. The animal is very powerful and is able to leap a considerable distance. Mr. Arthur Adams, a celebrated conchologist, thus describes its method of leaping: “Planting firmly its powerful, narrow operculum against any resisting surface, it insinuates it under the edge of its shell and by a vigorous effort, throwing itself forwards, carrying its great heavy shell with it, the animal rolls along in a series of jumps in a most singular and grotesque manner.” The eyes of the animal are greatly developed. The shells of Strombus vary greatly in form and color. In some the outer lip is simply turned over while in others it is modified by little spines or projections. The aperture is frequently colored pink, purple or yellowish. The large Strombus gigas is used in carving cameos, its shell being made up of several layers of different colors. It is also ground to powder for the manufacture of porcelain and in the West Indies the animal is used as an article of food.