A family of shells closely related to the limpets is the Fissurellidæ, or keyhole limpet, distinguished from the last family by having a slit or foramen in the apex of the shell, through which the waste products of digestion are discharged. This slit resembles a key-hole and for this reason they are called key-hole limpets. The shells of Fissurella are generally rougher than those of Patella and they live, as a rule, in warmer seas. In habits the key-hole limpet resembles the limpet, living in one rocky place and making excursions for food. In the young shell the spire is without a perforation, this appearing as the shell increases in age. There are over one hundred species of key-hole limpets, several handsome species of which inhabit Florida and the West Indies. The Haliotis or abalone shells abound in many parts of the world and are widely known for their beauty. The largest and finest shells live on the coast of California where they attain a length of ten inches. The shells are flat, though made in the form of a spiral and are perforated near the edge of the last whorl, which is many times the size of all the rest combined, and through this perforation the water from the gills, together with the waste products of the animal, are poured out. As the shell increases in size the old holes are filled up and new ones are formed. The inside of the shell is resplendent with iridescent colors, particularly about the region of the huge muscle scar, and when the outside is polished they become objects fit for the palace of a king. A large part of the mother-of-pearl is furnished by these shells and a vast number are annually exported for the purpose of making pearl buttons. In England they are called “Ormers” but the correct name, if we translate the generic title, is “Sea-ear” or ear-shells. To the Chinese the abalone is an object of great economic importance and they gather them in large quantities, dry the animals and use them as food, principally in the form of soup, which is said to be very delicious. The abalone clings to the rocks with terrible power and many a lonely fisherman has been drowned while gathering this mollusk, by getting his fingers caught between the shell and the rock. [Illustration: SOME SNAILS OF THE OCEAN. FROM COL. CHI. ACAD. SCIENCES.] Top row: Strombus puris dianae (Philippines). Bulla ampulla (Philippines). Harpa nobilis (Philippines). Second row: Littorina angulifera (United States). Fissurides listeri (United States). Third row: Nerita peloronta (Florida). Crepidula fornicata (United States). Terebra lamarckii (Sandwich Islands). Turbo petholatus (Indian Ocean). Fourth row: Nitra politificalis (Indian Ocean). Haliotis assimilis (California). Cerithalma aluco (East Indies).