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* PLESIOSAtTBTJS. vhioli 116 PLEURISY. attained a Tlic genus yolhomtirus. w IciiL'th of about ten feet, had a lonjr lluttencd skull and small eves near the middle of the head. The teeth were numerous, small and re^'ular in the posterior portion of the jaws, but larpe and reeurved. like spreadin- lusks, in the front J'IcsUmiiinis had a proportionately smaller head of triansiilar form and a neek whieh m some species exceeded in length the remainder of the bodv. and which was supported in the difTerent siieeies bv from 25 to 40 cervical vertcbne. The teeth "arc not so numerous as in Xothosaurus, and are larger, recurved, and interlocking. The pelvic and pectoral limlis are remarkably similar to each other in form, and the phalanges of both were imbedded in cartilage which filled out the form of the paddle just as in the ichthyosaurs. These creatures varied from 10 to 20 feet in length, and they must have been very abundant in "the Liassic'seas of England and Germany, where finelv preserved skeletons of them have been obtained. Twentv-five species are known m the Lias of England alone. Pliosaurus is a gigantic plesiosaur with a skull nearly five feet long and teeth twelve inclics long, found in the English Upper .Jurassic, and it is possibly a synthetic tvpe between the ichthyosaurs and the p'lesiosaurs! American representatives of the Iilesiosaurs have been found in the Upper .Jurassic beds of Alabama, Kew Jersey. Ivansas. and Wyoming, and have been described under the names Cimoliosaurus. Megalosaurus. Elasmo- saurus, Doliehorhync!ioi)s, etc. A skeleton of Cope's EInsmosauniii from the Upper Cretaceous of Fort Wallace. Jansas. lacking the head, nieas- ires 42 feet in length, of which the neck, with 72 vertebrie. occupies 22 feet. Some of the American examples have afforded interesting evidence of the feeding habits of these creatures. Stones of various sizes from one-quarter inch to four inches diameter were found in the position of the stomach, and are sui)posed to have been swallowed by the animals as aids to digesti<m. One specimen had 12.i such stones in its stomach. Plesiosaurs, as Cuvier expressed it, combine the paddles of a whale, the head of a lizard, and a long neck like the body of a serpent. They were powerful animals, swimming freely about the shallow seas of .Jurassic and Cretaceous times, and feeding upon the fish and smaller marine reptiles, for preying upon which their lung necks and numerous spreading teeth admirably fitted them. Bibliography. Von Zittel and Eastman, Textbook of Pnlwontolofrji. vol. ii. (Xew York and London. 1902.) : Williston. "A Kew Plesio- saur," etc., TravsnrtioDS of the Kansas Academy of Science, vol. xii. (Topeka, 1890) ; id.. "An Interesting Food Habit of the 'Plesiosaurs." Transactions of the Kansas Academt/ of Science, vol. xiii. (ToiM'ka. 1893) : id.. "Xorth American Plesiosaurs. Part I.." Field Cnliimhian Museum, Puhlieation 73, Geoloriical Series, vol. ii., No. 1 (ChiinL'o. 1003). PLESSIS, ples'sA', .JosEru OcTxra (1763- 182.5). A Roman Catholic prelate of Canada. He was born at Montreal. He entered the priest- hood in 1801, was appointed coadjutor to Mgr. Denauet. Bishop of Quebec, and succeeded to the bishopric upon the death of that prelate in 1800. He obtained a royal charter for Nicolet College, where he instituted classical training, and found- ed the primary schools of Quebec. The British Government did not immediately recognize his elevation to the office of bishop, claiming the right of nomination to the office within the prov- ince which the French Government had formerly possessed. But the Bishop successfully main- tained his position in the controversy, and in 1818 he was summoned to the Executive Council of Canada by his episcopal title. In 1818 Quebec was made an archbishopric, but the Government never gave recognition to this titular ailvance- ment. He always showed great attachment to the British Crown and enthusiastically supported the Imperial relation. Consult his Life by Fer- land (Quebec. 1804) ; and Kingsford, History of Canada (Toronto and London, 1888-98). PLEURA (Neo-Lat., from Gk. jrXei/pd, rib, side). The name of a very delicate serous mem- brane externally investing the lung, which, after inclosing the whole organ, except at its root, where the great vessels enter it, is reflected upon the inner surface of the thorax or chest. Tliat ])ortion of the pleura which is in contact willi the surface of the lun<' is called the pleura pulmonalis, or visceral layer, while that which lines the interior of the chest is called the pleura costalis, or parietal layer, and the space inter- vening between these two layers is called the carity of the pleura. Each pleura is a closed sac, and quite independent of the other. The central interspace between the right and left pleura; is termed the mediastinum, and contains all the viscera of the thorax excepting the lungs. The inner surface of each jileura is .smooth, glistening, and moistened by a serous fluid ; the outer surface is closely adherent to the surface of the lung, to the root's of the pulmonary vessels as they enter the lung, to the upper surface of the diaidiragm. and to the walls of the chest. The lobes of the lungs are separated from one another by involutions or in-foldings of the vis- ceral layer. The use of these serous sacs is j much the same as that of the peritoneum (q.v.) ; each pleura retains the lung and to a certain I extent the greater vessels in position, while it at ] the same time facilitates, within certain limits, j the movements of those parts which are essential to the due performance of the act of respira- I tion. PLEURACANTHUS (Xco-Lat., from Gk. | ■K ,p6v, pleuron. rib + arai-ea, akantha, spine). A fossil shark-like fish found in the Carbonif- 1 erous and Permian rocks of North America, Europe, and Australia. The body was long and tapering, with a linguate diphycereal caudal fin. The dorsal fin extended almost the entire length of the back and was separated from the up|ier lol)e of the caudal fin by only a slight notch. On the top of the head was a long, posteriorly di- rected strong spine, which was hollow and armed with longitudinal rows of barbs. The pectoral and pelvic fins were large and there were two small anal fins. Several complete skeletons of this fish have been found in the European Car- boniferous rocks. PLEURISY (Fr. pleurcsie. from Lat. pleuri- sis. plcuritis, from Gk. TrXeupins. pleurisy, from irXeupd, pleura, rib). An inflammation of the pleura, the serous membrane investing the lungs. This membrane, like the pericardium (q.v.) and the peritoneum (q.v.). consists of two layers, a visceral and a parietal, the former clo.sely at- tached to the lungs, and the latter applied to