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* PLEISTOCENE PERIOD. 113 PLESIOSAURUS. rise to many lines of raised lieaclies which are represented in the terraces in the Hudson Valley and along Lake Champlain. A similar submer- gence occurred along the I'acitic coast. The animal and plant life of the Pleistocene was in some cases decidedly Arctic in its nature, but many species existed which are still living. The mammals were especially abundant. Those of North America included mastodons, elephants, tapirs, horses, and sabre-toothed tigers, as well as a giant beaver; while in South America the sloths were e.xtraordinarily developed, some being equal in size to an elephant. In Europe the remains of the mammoth, hairy rhinoceros, the great cave-bear, and the Irish deer have been found. Bibliography. Stone, "The Glacial Gravels of Maine and their Associated Deposits," United States Geological Survey, Bulletin S-i (Washing- ton, 1891) ; Leverett, "The Illinois Glacial Lobe," United States Oeologieal Surrey, Bulletin 38 (Washington, 1899) ; Chamberlain, "Preliminary Paper on the Terminal Moraine of the Second Glacial Epoch," United States Oeologieal Survey, Third Annual Rc/iort (Washington,' 1883). See also various articles in the volumes of the American Geologist, Journal of Geology, Ameri- can Journal of Hnence, Bulletin of the Geological Society of America, etc. See Glacial Period. PLENER, pla'ner, Ernst, Edler von (1841- — ). An Austrian statesman, son of Ignaz von Plener. He was born at Eger, and was educated at Vienna and Berlin. He served in the diplomatic corps (1865-73), and then entered the Imperial Diet, where he joined the Left, and supported An- drassy's policy in the Balkans (1878). He suc- ceeded Herbst as head of the German Liberals, both in Pragtie and in Vienna, and in 1888 wag chosen leader of the partv called "United German Left." From 1893 to 1895 Plener was a mem- ber of Taafe's Cabinet as Minister of Finance, and in 1900, after five years at the head of the Court of Accounts, he entered the House of Lords. He wrote on English economic conditions, and a .sketch of Ferdinand Lasalle (1884), as: well as some valuable speeches delivered in the Bohemian Diet on the Bohemian school and language question (1886). PLENER, Ic.NAZ, Edler von (1810 — ). An Austrian states- man. He was born in Vienna, studied law, and entered the governmental service, in which he showed much ability in finance. In 1859 he was made privy councilor; a year after- wards received the portfolio of finance and planned various important reforms, reviving the Bank Acts and the Minis- try of Commerce before his resignation in 1865; and in 1867 he entered the Liberal Centralist Cabinet of Giskra as Min- ister of Commerce. This post he held until the fall of the Cabinet in 1870. He was a member of the Lower House until 1873, when he was ap- pointed to the House of Lords. Plener was an ardent defender of a personal income tax. which he proposed in 1880 as a solution of financial dif- ficulties. PLENIPOTENTIARY. See E.woY. PLEROME ( from Gk. irXr/pufw., plerOma, a fill- ing). The central embryonic region in stems and roots. It develops into the stele, in which the vascular sy>tem appears. See Stem. PLESHTCHEYEFF, plesh-clia'yef, Alexei (1825-93). A Russian poet, born at Kostroma, and educated at the L^niversity of Saint Peters- burg. Ilis first volume of poetry, published in 1845, was well received. In 1849 he became in- volved in a political complication, was accused of conspiracy against the Czar, and sentenced to be shot, but Nicholas I. commuted the death sentence to banishment to Orenburg, where Pleshtcheyeff enlisted in the army as a private soldier. Having distinguished himself in the Caucasus during the Crimean War, he was par- doned in 1857, and in 1872 made his home in Saint Petersl)urg. From this time he produced much original poetry and also translated poems of Heine, Byron, and Tennyson. In 1887 he published a complete collection of his verse. PLESIOSAU'RUS (Neo-Lat., from Gk. tXtio-ws, plesios, near + (raOpos, sauros, lizard). A peculiarly interesting fossil marine reptile of the order Sauropterygia, found in the Liassic rocks of Europe. The order Sauropterygia com- ])rises a number of reptiles which began as small amphibians in the Trias and culminated in the Cretaceous as larger forms fully adapted to marine habits of life. They hail short, thick, lizard-like bodies, very long, flexible necks, small lieads, and powerful tails. The early members had elongated limbs adapted for crawling on land, which became shortened and assumed pad- dle-like form in the later genera, but which never so thoroughly degenerated to fin-like organs as did those of the analogous group of iehthyosaurs ( q.v. ) . Two families are recognized : Notho- sauridce. comprising small, more primitive forms, having five-toed feet with the nornuil number of finger bones or phalanges ; Plesiosauridce, com- prising large animals with paddle-shaped limbs Outline of Plesiosa of skull. THE PLESIOSAUEUS. urns dolichodeirus, fossilized skeleton, and enlarged view and the digits lengthened by an increased number of phalanges, and with the pectoral girdle enlarged to form a protective covering for the thorax. Lariosaurus and Nothosaurus from the Triassic of Europe are the important genera of the first family; and Plesiosaurus from the Liassic of Europe and Cimoliosaurus from the Cretaceous of America and New Zealand are representative of the second family.