Shell
in zoölogy, the hard calcareous substance which either protects the testaceous mollusca externally, or supports certain species of them internally.
SHELL Though shells, properly so called, which form the habitation of testaceous animals are sometimes confounded with the shelly coverings which protect the crustacea (crabs and their numerous allies), a very obvious and striking difference exists between them, as well as between the kinds of animals which respectively inhabit them. The shells of testacea are composed of carbonate of lime, combined with a small portion of gelatinous matter; they are, in general, permanent coverings for their inhabitants; and the animal is of a soft substance, without bones of any kind, and attached to its domicile by a certain adhesive property.
On the other hand, those animals which are defended by a crustaceous covering cast their shells and renew them annually; while the animals themselves are of a fibrous texture, with articulated limbs, and protected, as it were, by a coat of mail.
Shells are divided into Multivalves, Bivalves, and Univalves. The first order, Multivalve, is made up of shells consisting of more shelly parts or pieces than two.
The second order, Bivalve is made up of shells having two parts or valves, generally connected by cartilage or hinge; as in the cockle and mussel. The third order, Univalve, is made up of shells complete in one piece-as in the periwinkle and the whelk-and they are subdivided into shells with a regular spire, and those without a spire. The shells composing this order are far more numerous than those of the two preceding, both in genera and species. The spire is a prominent feature of the Univalve; and on its being lengthened or elevated, shortened or depressed, etc., depends much of the generic and specific definitions.
Shells increase in size by the deposition of new layers internally on those already formed. Each new layer extends more or less beyond the margin of the layer mal becomes older its shell becomes larger to which it is applied, so that as the aniand thicker. The outer surface is generally covered by a thin layer of membranous or horny matter, named the epicover dermis, and the inner surface is often covered with a layer of a pearly nature.
In military usage the name shell is given to a hollow vessel of metal containing gunpowder, or other explosive compound, so arranged that it will explode at a certain point and spread destruction around by the forcible dispersion of its fragments. The invention of this missile, formerly called a BOMB (q. v.), cannot be accurately traced. Shells were employed in A. D. 1480 by the Sultan of Gujerat, and by the Turks at the siege of Rhodes in 1522. The Spaniards and Dutch both used them during the war SHELTER AND HOUSING should be deprived of the children of his second marriage , Shelley left England in March, 1818, March, 1818, and the whole short relife was passed in Italy, After staying for some time with Lord Byron at Venice he proceeded to Naples; Rome; and from Rome he went to Florence and Leghorn, and finally settled at Pisa. On July 8, 1822, he was sailing with a Mr. Williams in the Bay of Spezia when both were drowned by, as was believed, the upsetting of the boat through a sudden squall.
His body was, according to Italian law, seashore.