Page:EB1911 - Volume 04.djvu/381

 to ventral valve. FAMILIES.—

Class II.

'''ORDER III. Protremata''' (Beecher).—Articulate Brachiopoda, with pedicle-opening restricted to ventral valve, and either open at the hinge line or more or less completely closed by a pseudo-deltidium, which may disappear in adult. The pro-deltidium originating on the dorsal surface later becomes anchylosed with the ventral valve. FAMILIES.—

'''ORDER IV. Telotremata''' (Beecher).—Articulate Brachiopoda, with the pedicle-opening, confined in later life to the ventral valve, and placed at the umbo or beneath it. Deltidium present, but no pro-deltidium. Lophophore supported by calcareous loops, &c. FAMILIES.—

Affinities.—Little light has been thrown on the affinities of the Brachiopoda by recent research, though speculation has not been wanting. Brachiopods have been at various times placed with the Mollusca, the Chaetopoda, the Chaetognatha, the Phoronidea, the Polyzoa, the Hemichordata, and the Urochordata. None of these alliances has borne close scrutiny. The suggestion to place Brachiopods with the Polyzoa, Phoronis, Rhabdopleura and Cephalodiscus, in the Phylum Podaxonia made in (vol. xix, ninth edition, pp. 440-441) has not met with acceptance, and until we have a fuller account of the embryology of some one form, preferably an Inarticulate, it is wiser to regard the group as a very isolated one. It may, however, be pointed out that Brachiopods seem to belong to that class of animal which commences life as a larva with three segments, and that tri-segmented larvae have been found now in several of the larger groups.

Distribution.—Brachiopods first appear in the Lower Cambrian, and reached their highest development in the Silurian, from which upwards of 2000 species are known, and were nearly as numerous in the Devonian period; at present they are represented by some 140 recent species. The following have been found in the British area, as defined by A. M. Norman, Terebratulina caput-serpentis L., Terebratula (Gwynia) capsula Jeff., Magellania (Macandrevia) cranium Müll., M. septigera Lovén, Terebratella spitzbergenensis Dav., Megathyris decollata Chemn., Cistella cistellula S. Wood, Cryptopora gnomon Jeff., Rhynchonella (Hemithyris) psittacea Gmel., Crania anomala Müll., and Discinisca atlantica King. About one-half the 120 existing species are found above the 100-fathoms line. Below 150 fathoms they are rare, but a few such as Terebratulina wyvillei are found down to 2000 fathoms. Lingula is essentially a very shallow water form. As a rule the genera of the northern hemisphere differ from those of the southern. A large number of specimens of a species are usually found together, since their only mode of spreading is during the ciliated larval stage, which although it swims vigorously can only cover a few millimetres an hour; still it may be carried some little distance by currents.

Undue stress is often laid on the fact that Lingula has come down to us apparently unchanged since Cambrian times, whilst Crania, and forms very closely resembling Discina and Rhynchonella, are found from the Ordovician strata onwards. The former statement is, however, true of animals from other classes at least as highly organized as Brachiopods, e.g. the Gasteropod Capulus, whilst most of the invertebrate classes were represented in the Ordovician by forms which do not differ from their existing representatives in any important respect.

A full bibliography of Brachiopoda (recent and fossil) is to be found in Davidson’s Monograph of British Fossil Brachiopods, ''Pal. Soc. Mon.'' vi., 1886. The Monograph on Recent Brachiopoda, by the same author, ''Tr. Linn. Soc. London'', Zool. ser. ii. vol. iv., 1886–1888, must on no account be omitted.

 BRACHISTOCHRONE (from the Gr. , shortest, and  , time), a term invented by John Bernoulli in 1694 to denote the curve along which a body passes from one fixed point to another in the shortest time. When the directive force is constant, the curve is a (q.v.); under other conditions, spirals and other curves are described (see ).

 BRACHYCEPHALIC (Gr. for short-headed), a term invented by Andreas Retzius to denote those skulls of which the width from side to side was little less than the length from front to back, their ratio being as 80 to 100, as in those of the Mongolian type. Thus taking the length as 100, if the width exceeds 80, the skull is to be classed as brachycephalic. The prevailing form of the head of civilized races is brachycephalic. It is supposed that a brachycephalic race inhabited Europe before the Celts. Among those peoples whose heads show marked brachycephaly are the Indo-Chinese, the Savoyards, Croatians, Bavarians, Lapps, Burmese, Armenians and Peruvians. (See .)

 BRACHYLOGUS (from Gr. , short, and  , word), title applied in the middle of the 16th century to a work containing a systematic exposition of the Roman law, which some writers have assigned to the reign of the emperor Justinian, and others have treated as an apocryphal work of the 16th century. The earliest extant edition of this work was published at Lyons in 1549, under the title of Corpus Legum per modum Institutionum; and the title Brachylogus totius Juris Civilis appears for the first time in an edition published at Lyons in 1553. The origin of the work may be referred with great probability to the 12th century. There is internal evidence that it was composed subsequently to the reign of Louis le Débonnaire (778–840), as it contains a Lombard law of that king’s, which forbids the testimony of a clerk to be received against a layman. On the other hand its style and reasoning is far superior to that of the law writers of the 10th and 11th centuries; while the circumstance that the method of its author has not been in the slightest degree influenced by the school of the Gloss-writers (Glossatores) leads fairly to the conclusion that he wrote before that school became dominant at Bologna. Savigny, who traced the history of the Brachylogus with great care, is disposed to think that it is the work of Irnerius himself (Geschichte des röm. Rechts im Mittelalter). Its value is chiefly historical, as it furnishes evidence that a knowledge of Justinian’s legislation was always maintained in northern Italy. The author of the work has adopted the Institutes of Justinian as the basis of it, and draws largely on the Digest, the Code and the Novels; while certain passages, evidently taken from the Sententiae Receptae of Julius Paulus, imply that the author was also acquainted with the Visigothic code of Roman law compiled by order of Alaric II.

 BRACKET, in architecture and carpentering, a projecting feature either in wood or metal for holding things together or supporting a shelf. The same feature in stone is called a “” (q.v.). In furniture it is a small ornamental shelf for a wall or a corner, to bear knick-knacks, china or other bric-à-brac. The word has been referred to “brace,” clamp, Lat. bracchium, arm, but the earliest form “bragget” (1580) points to the true derivation from the Fr. braguette, or Span. bragueta (Lat. bracae, breeches), used both of the front part of a pair of breeches and of the architectural feature. The sense development is not clear, but it has no doubt been influenced by the supposed connexion with “brace.”

 BRACKET-FUNGI. The term “bracket” has been given to those hard, woody fungi that grow on trees or timber in the form of semicircular brackets. They belong to the order Polyporeae, distinguished by the layer of tubes or pores on the under surface within which the spores are borne. The mycelium, or vegetable part of the fungus, burrows in the tissues of the tree, and often destroys it; the “bracket” represents the fruiting stage, and produces innumerable spores which gain entrance to other trees by some wound or cut surface; hence the need of careful forestry. Many of these woody fungi persist for several years, and a new layer of pores is superposed on the previous season’s growth.

<section end="Bracket-Fungi" /> <section begin="Bracklesham Beds" />BRACKLESHAM BEDS, in geology, a series of clays and marls, with sandy and lignitic beds, in the Middle Eocene of the Hampshire Basin, England. They are well developed in the Isle of Wight and on the mainland opposite; and receive their name from their occurrence at Bracklesham in Sussex. The thickness of the deposit is from 100 to 400 ft. Fossil mollusca are abundant, and fossil fish are to be found, as well as the Palaeophis, a sea-snake. Nummulites and other foraminifera also occur. The Bracklesham Beds lie between the Barton Clay above and the Bournemouth Beds, Lower Bagshot, below. In the London Basin these beds are represented only by thin<section end="Bracklesham Beds" />