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* RHYNCHOCEPHALIA. lU RHYTHM. legs were strong and the feet were provided with five cliiwed toes and adapted to progress on laiul. A suborder, Pclycosauria, includes several curi- ous though imperfectly known genera in vliich the anterior teetli are different from the posterior and the dorsal vertebra; are furnished with greatly elongated neural spines. The lilii/ncho- THE HHYNCHOCEPHALIC SKULL. CraEium of llyperodapedon Gortloni: 1, superior as- pect ; 2, lateral aspect ; 3, mandibular symphysis. cephalia vera includes the most highly specialized forms, which attain their maximnm of evolu- tion and widest geographic distribution in late Triassic time. They are cliaracterized by more complete ossification of the skeleton, by reduc- tion of the abdominal ribs, and by having uni- form marginal teeth. BiBLioGRAniY. Von Zittel and Eastman, Text- book of Paleontology, vol. ii. (London and New York, 1902). BHYN'CHONEL'LA (Neo-Lat. nojn. pi., from C4k. I'lijyxoi, rhi/nclws, snout). A genus of hrachiopods, scarce but widespread in modern seas, but very abundant anciently, and represent- ed in almost every geological formation from the Ordovician u]iward. About 600 species have been described, mostly from the ]Iesozoic rocks, of which the .Jurassic and Cretaceous groups are especially prolific. Most of the ancient forms are doubly convex shells with prominent though small ventral beaks, and with surfaces marked by strong, usually angular radial plications, and with a more or less elevated median fold and sinus. The structure of the shell in most genera is non-punctate, a character by which the species may most readily be distinguished from the closely similar species of Terebratulidaj. Con- sult: Hall and Clarke, Paleoiitology of Neiu York, vol. viii., part ii. (Albany, 1894) ; Davidson, "Monograph of the Recent Brachiopoda," Trans- actions of the Linnean Societi/, vol. iv. (London, 1886-88). BHYOLITE (from Gk. piJaJ, rhyax, stream, especially of lava, from fx^p, rhein, to flow -|- l8ot, lithos, stone), Lipasite. Nevadite. An igneous rock of porphyritic texture and siliceous composition, generally with a crumply, banded (rhyolitic) texture, due to the arrangement of its constituent minerals by flowage. Khyolites are also frequently glassy, vesicular, scoriaceous. or pumiceous. When compact and massive, rhyolites are designated as rhyolite porpliyries ( formerly called quartz porphyries, and then supposed to be of geological age older than the Tertiary). In chemical composition rhyolites have about the same range as the granites. They average: Silica, 75 per cent.; alumina, 13 per cent.; sesquioxide and protoxide of iron, each 1 per cent.; oxide of lime, 1 per cent.; oxide of sodium, 3 per cent.; oxide of potassium, 6 per cent. Varieties rich in oxide of sodium are designated soda-rhyolites (panlclleritcs). Rhyolites arc for the most pari; surface lavas or are intruded in other rocks as dikes or sills. Very extensive areas of rhyolite are found in the Cordilleran mountain sj'stem of the Western Hemisphere. Khyolites when of unusually coarse grain are now designated by the variety name, Nevadite. RHYS, rOs, EHNE.ST (1859—). An English author, born in London, July 17, 1859. He was educated at schools in Carmarthen, South Wales, at Bishop-Stortford and at Nevcastle-on-Tyne, and became a mining engineer (1877). In 1S85 he abandoned the profession for general litera- ture. In 1887 he came to the United States on a lecturing tour. His writings on Welsh subjects are popular and are to be distingiiished from those of the profound Celtic scholar John Rhys (q.v.). He edited the Camelot series of popular reprints and translations (05 vols., 1886-91); Dekker's Plai/s for the Mermaid Series (1888) ; The Lyric Poets (12 vols., 1894-99); Literary Pamphlets (1897) ; and other works. His writ- ings include : The Great Coekney Trayedy ( 1891 ) ; .4 Loudon Rose and Other Rliymes (1894) ; Wclsli, Ballads and Other Poems (1898) ; Frederick Lord Leiyhlon, a biography (1898, which had been pre- ceded by an earlier studj' in 1895) ; and two romances, The Fiddler of Came, having a Welsh heroine (1896), and The Whistling Maid (1900). RHYS, .John (1840—). A Welsh author and professor of Celtic at Oxford since 1877. He was born in Cardiganshire in 1840 and educated at Bangor Normal College, Jesus College, Oxford, the Sorbonne, Heidelberg, and Leipzig. In 1871 he became school inspector for Flintshire and Denbighshire; fellow of Jesus College in 1881; Hibbert lecturer, 1886 ; Rhind lecturer on archae- ology in Edinburgh, 1889; and has seen service on numerous commissions on education, reforms and land movements connected with Wales. His works are: Lectures on Welsh Philology (1877); Celtic Britain (1882); Celtic Eeathendom (1886) : Studies in the Arthurian Legend (1891) ; Inscriptions and Language of the Sortltern Picts (1892) ; lihind Lectures on the Early Ethnology of the British Isles (1890-91) ; CeUic Folk-Lore (1901) ; and in conjunction with Mr. D. Bryn- mor-Jones, The Welsh People (1900). Professor Rhys has also cooperated in the production of several important editions of Welsh texts and his contributions to Celtic scholarship have been various and important. To his native and un- surpassed knowledge of Wales and of the Welsh language he has added wide research in the other languages of the Celtic group, and in the history and antiquities of the Celtic peoples. Besides doing valuable linguistic work in early Welsh and Manx, he has made himself the chief living authority on the Ogam inscriptions. His studies on folk-lore, mythology, and religion have been learned and brilliant, but rather bold in conjec- ture. The editions of Welsh texts which he has brought out in collaboration with Professor Mor- ris Jones and Mr. J. Gwenogvryn Evans are models of accurate editing. RHYTHM (Lat. rhythmus. from Gk. jivBixis, rhythmos, rhythm, time, measure, from ^etK, rhein, Skt. sru, to flow). A complex mental process which has been defined, from different points of view, as a temporal perception and as a regulated emo- tion. Objectively regarded, it is a regularly measured and regularly stressed movement in i