LABYRINTHODONTA, or STEGO CEPHALI, a group of primitive four-footed animals, forerunners of modern amphibians and reptiles, whose remains are found fossil in Peruvian, Carboniferous and Triassic strata, and which are the oldest known lung-breathing terrestrial quadrupeds. They were first discov ered through finding their footprints imprinted in the Triassic rocks (Keuper •beds) of Ger many, long before the actual fossilized remains were brought to light. The footprints were described at first as those of a hypothetical form to which the name Cheirotherium ('hand beast*) was given. As geological science and research progressed, the remains of the laby rinthodonts were discovered, when a compar ison of their structure with the footprints showed that some of the latter were made by these creatures,- many of the tracks, however, are unidentified. Later, when a great variety of related remains had been discovered, the term Labyrinthodonta, which relates to the curi ous °labyrinthine* infoldings of the enamel-wall of the teeth, was restricted to a single group or suborder (also called Stereospondyli) within the general amphibian order Stegocephalia. This suborder contains highly developed and mostly large forms, characterized by the com plication in tooth structure above mentioned, and by co-ordinate anatomical distinctions. The principal genera are Lazomma, Trematosaurus, Metopias, Capitosaurus, Mastodonsaurus and Labyrinthodon, the last including the most re cent forms of the Upper Trias, at the close of which period the group appears to have be come extinct. See STEGOCEPHALIA.
LAC is the product of one of the scale insects (Coccus, or Tachardia, lacca) of the family Coccida, which is the source of an im portant Oriental industry. This species, like other scale-insects, multiples with amazing rapidity, and feeds in compact colonies of tens of thousands, carrying the twigs of certain trees, especially the banyan or °religious" fig and related species of Fious, the dhak 'Butea frondosa) and some other trees in India and Assam, and on privet trees in Yunnan and Szchuen provinces in southwestern China. In serting their beaks into the bark females of these insects suck the sap, a large part of which passes out as excrement, transformed into a sort of resin that accumulates over the insect's back and forms the 'scale." The scales of the crowded insects coalesce at their edges into a continuous layer over the slender branch on which they are feeding, and such a branch, cut off, is known as 'stick lac." By tieing a few of these sticks on fresh parts of trees the natives induce the insects to spread to and over fresh branches, and thus•obtain two crops a year. The industry is a very ancient one and gives a living to a large number of people; and the value of lac products exported from India alone approaches 35,000,000 of rupees (about $17,500,000) annually. The best lac comes from Bengal and the central provinces.
The original method of preparing the lac for use and market was by pulverizing the in sect-covered twigs, at the proper time, and placing the fragments in hot water. This separated the scales from the wood, softened the resin, and dissolved the coloring-matter of their interior tissues, especially strong in the egg-sacks. The remains of the insects are then taken out and dried; and this operation of washing and drying is repeated until the resin from the melted scales is (or ought to be) entirely colorless. The mass is then put into a bag of coarse cotton cloth which is held near enough a fire to melt the lac, and is squeezed by twisting. The melted resin drips on small sticks arranged to receive it, and con geals into thin, light-colored, transparent flakes called shell-lac, the shellac of commerce. Large and small drops falling on the ground form button-lac, lump-lac, and so forth. Latterly this work has been done by machines made to grind the sticks, and melt and wash the mate rial in steam-heated apparatus, which quickens the process and improves the product.
The water in which the first washings are made is deeply reddened by the dissolved color ing-matter in the insects. This water is saved, strained and evaporated, or cleared by the aid of alum, and the residue is deposited. This, when dried, is molded into cakes that furnish a rich dye. Previous to the invention of aniline colors this was very valuable, but now, like cochineal, it has nearly disappeared from trade. It furnishes, however, the basis of many "lake" tints among artist's colors, particularly the exquisite carmine-lake. "Lake" is a modified form of the Sanskrit (and modern Hindu) word lak, or lac, which means a hundred thou sand, and here refers to the multitude of insects in a colony; it is also familiar to us in the financial term lakh, meaning 100,000 rupees.
Lac is of great value for making varnish, because easily dissolved, furnishing a hard coating susceptible of fine polish, and easily taking a dye. The Indian, Burmese and Chi nese use it for making and coating ornaments, and various artistic objects, usually rich in color. It also enters into the composition of the fancy sealing wax sold by stationers, and serves other useful purposes; hut it must not be con founded with lacquer (q.v.), an Oriental vege table product that resembles lac, when applied as a coating of boxes, bowls, etc.
LAC, or LAK, from the Sanskrit lakshii, or laksha, that is, 100,000. In the East Indies it is applied to the computation of money. Thus, a lac of rupees is 100,000 rupees. A lac is equal to about $46,350. A lac of Sicca rupees was equal to about $50,000; 100 lass, or 10,000,000 rupees, make a crore. In 1835 the British government remodeled the currency of India, establishing a more uniform system, and the value of the rupee is now fixed at 32 cents (IS to the sterling ,i), divided into 16 annas of 12 pies. ,