TEILLIUM now placed in a suborder of the lily family. They are perennial herbs with a short tuber- like rootstock, from which rises a simple, na- ked stem, usually less than a foot high, bear- ing at its summit a whorl of three ovate or rhomboid, netted-veined leaves, above which is a terminal flower, usually large, succeeded by an ovate, purple or red, three-celled berry. The trilliums, of which there are about a dozen species, are among the most striking of our spring flowers; their symmetrical struc- ture and the beauty of the flowers in most species are interesting and attractive; they grow in rich moist woods or bogs, some ex- tending from Canada to Georgia, one being peculiar to the far southern states, and two or three to the Pacific coast. The plants have received various common names, among which are three-leaved nightshade, wakerobin, birth- root, bethroot, and Indian balm. The great- flowered trillium (T. grandiflorum) is the TRILOBITE 867 Large-flowered Trillium (Trillium grandiflorum). showiest species ; its pure white flowers, often 3 in. across, and becoming rose-colored with age, are erect and raised above the leaves on a peduncle 2 to 3 in. long. The purple trillium (T. erectum) has rather smaller, dull purple flowers. The red-fruited species (T. erythro- carpum) has its white petals marked at the base with pink or purple stripes. The nodding trillium hides its flowers beneath the leaves by the recurving of its stalk. T. sessile often has its leaves blotched with two shades of green ; and the related T. discolor, the southern spe- cies, has very ornamental foliage from being variegated with green and brown or purple. All flourish well in the garden, T. grandi- florum being especially ornamental ; large num- bers of its tubers are sent to Europe, to be sold by the bulb dealers. The roots of tril- lium contain an acrid principle analogous to senegine and saporvine, as well as a volatile oil, resin, and tannic acid. They are astringent, and are said to be tonic and expectorant. TRILOBITE (Gr. rpeZf, three, and Ao/3df, lobe), the name of a group of fossil crustaceans, so called from the three lobes into which the body is divided. They do not correspond exactly to any living group, but, according to Burmeister ("Organization of Trilobites," Ray society's publications, 4to, London, 1846), were a pecu- liar family of crustaceans, nearly allied to the existing phyllopoda (like apus and branchipus), and forming a connecting link between these and the entomostracan poecilopoda (like ar- gulus, caligus, and other parasites called fish lice) ; they come nearest to phyllopods, espe- cially in the double large eyes, undeveloped antennae, and soft membranous feet, and near- est of all to branchipus ; a marked resem- blance in the form of the limulus (king crab, or common horseshoe of our coasts), especially the larva, is also observed to that of many species of trilobites. (See KING CRAB.) The general form of the animal is oval, divided into three well defined regions, the head or buckler, the thorax, and the abdomen or py- gidium, the last two composed of semicircular plates or segments, varying in number, by whose movements the animal could roll itself into a ball like the common wood louse and pill bug (oniscus and armadillo). Each of these three divisions presents three lobes lim- ited by two longitudinal depressions ; the head is generally the largest and considerably the widest, varying from one fourth to one half the total length, semicircular, with a Border often ornamented with granulations, depres- sions, and spines ; the middle portion is the glabella, the grooves which mark its lateral limit corresponding, according to Barrande, to the insertion of the jaws or first pair of feet ; the different pieces are united by distinct su- tures, which are important zoological charac- ters. Eyes have been denied to some genera ; some had eyes when young, but lost them when old; others had two well formed, xsompound, facetted, prominent eyes, which are often per- fectly preserved in the fossil state ; they are sometimes larger than half the length of the head, the greatest diameter being almost al- ways the longitudinal ; they had no simple eyes. Traces of a mouth have been distin- guished in a few ; no traces of antennae have been found, and they were probably short and feebly developed. The number of the thoracic segments varies in different genera and at dif- ferent stages of growth, but is constant in adults of the same species ; the terminal por- tions on the sides are the pleura, and are curved backward and sometimes very long ; traces of nine pairs of feet have been discovered, and they were doubtless soft, membranous, and leaf-shaped, as in phyllopoda. The pygidium was made up of segments like those of the thorax, but consolidated to form a posterior buckler ; it was usually semicircular, less long than wide, developed inversely to the thorax, and largest in the more recent genera. The shell had a thinner horny membrane cover-
