Page:The New International Encyclopædia 1st ed. v. 14.djvu/231

MUSSEL. 193 MTJSSET. It is gregarious and occurs in masses, closely crowded together, adiieriug to rocks, sand, and each otlier, l)y the very tough byssus, the whole 'beds' being thus lu'aetieally s|)un together. These beds are generally in shallow water, less than tliirty fathoms, and are often exposed at low tide. The shell is oblong with a terminal um- bone, and generally about three inches long by an inch and a lialf wide ; but under favorable conditions they may become six inches or even more in length. The outside of the shell is black, but inside it is pearly blue. When young, mu:r- , AMERICAN MAltl.NE MUSSELS. .1, common edible mussel iMytilus edulis) : b, horse or meadow mussel (Modiola modiolus) ; c, ribbed mussel (Mo- dioli plicatula). sels move about, but they soon anelior themselves by the byssus, and unless artilicially disturbed ■will I'emain fixed throughout life. So strong are the byssus-threads that these moUusks have been utilized as an aid in the strengthening of break- waters, tlie young mussels being planted on the rocks in myriads aud thus assisting in uniting the separate pieces into a rigid whole. The horse- mus.sels (q.v.) belong to the genus Modiola, which does not have the umbone terminal. They are more elongated than Mytilus and some spe- cies reach a much larger size. See Colored Plate of CI.AM.S AXD EdIP.LE MuSSELS. The other group to which the name mussel is given is the family Unionida', which are fresh- water mollusks of very wide distribution. The family is characterized by the possession of two adductor muscles and regular shells, with thick epidermis and thin nacreous layer, prominent external ligament, and a variable hinge. Up- ward of a thousand s])ecies have been named, a very large proportion of which occur in the United States, where the family is very abundant and widely distributed. It is still an open question as to what constitutes a valid species or even a genus in this family, though several genera, as Unio, Anodon, and Margaritana, are recognized. These fresh-water nmssels occur in lakes, ponds, and streams, generally in large num- bers together, and are sometimes eight inches or more in length, by four in breadth, but they are tisnally smaller and narrower. They are some- times used for food, but are tough and not very palatable. Their cliief im|inrtance lies in the fact that they frequently pro<lucc jiearls, and are indeed the only basis of th<' fresh-water pearl in- dustry. As high as $25,000 has been paid for a single mussel-pearl. (See Pe.rl). All of the Unionida" have a remarkable life-history, for the eggs when laid find their way into the mother's gills, where they remain until the young arc hatched. Although these young have a bivalve •shell, they are totally different from the adults and have a very simple structure. At this stage of development they are called 'glochidia' larviE. After leaving the maternal gills they attach themselves to the skin of a fish, where they give rise to an excrescence whieli gradually swells luitil it is a capsule big enough to see with the naked eye. These capsules are almost black and are usually seen on or near the fins of the host fish; they are often very numerous on a single lish. Within the capsule the glochidium lives until it finally assumes the adult form, when it breaks through the outer wall of the capsule and settles to the bottom as a miniature mussel. The distribution of the species is therefore mainly dependent on the activity of the fishes which serve as hosts. Fossil mussels are found in most geological formations from those of Ordovician age to those of recent time. The3' comprise the super- family Jlytilacea, containing the families Modio- lo])sida'. ilytilida>, and Dreissensiidie. The first, now entirely extinct, are essentially ancestral forms of the Mytilida', which range through De- vonian to recent formations. The Paleozoic species of this family belong mostly to the genus Modiola, which began in Devonian, was abundant in Jurassic and Tertiary time, and still persists as a common shell of the littoral zone of all seas. Mytilus began in the Triassic. Lithophagus or Lithodomus. the nuissel which bores cavities in limestone rock, has been recognized in Jlesozoic and Tertiary formations. The Dreissensiid* are of later origin, appearing first in the Tertiary. They are essentially fresh-water and estuarine mussels, and have probably evolved from Mytihis or a closely allied genus of the littoral zone in late Mesozoie or early Tertiary time. See Plate of Abalone, etc., and illustration under MoL- LUSK. MUSSELBURGH, mus'sd-bilr-6. A small seajiort town and Parliamentar}' burgh in the covmty of Edinburgh, Scotland, at the mouth of the Esk, 314 miles north by east of Dalkeith (Map: Scotland. F 4). Tanning, leather-dress- ing, and the manufacture of sail-cloths, nets, and .salt are carried on. The harbor at Fisherrow is frequented by coasting craft, and by small vessels from Holland and the Baltic. There are famous golf-links here. In the vicinity are in- teresting antiquities. Population, in 1891, 8888; in 1001," 11,704. MUSSEL-DIGGER. A popular name for the California gray whale. MUSSEL SCALE. A diaspine scale insect of the genus Mytilaspis, all of the species of which bear scales shaped like a mussel shell or the shell of an oyster. Several species are very injurious to vegetation. The so-called 'oyster-shell bark- louse' of the apple ( Mi/tilnspis pomorum) is a cosmopolitan enemy of apples and pears; and the long scale and the purple scale of the orange arc pernicious examples. MUSSET. my'sA', Ali-ked de (1810-57). A noted French poet, dramatist, and novelist, born in Paris, November 11, 1810. His father was a man of letters, and Alfred grew up in a literary atmos])here, was graduated with honors at the Coll&ge Henri Quatre. and published at twenty his first verses, Contes d'Espafiiie et d'ltalie '(1830). This, with Poesies d'irer.^s ( 1831 ) .and Le spectacle dans mi fauteuil ( 1832) , established his fame. The latter contained a