Pterichthys
a genus of Placoderms, discovered by Hugh Miller in the Sandstone. The head and ante- Old Red rior part of the trunk were defended by a buckler of large ganoid scales, united by sutures, the cuirass articulating at the sides with a back plate; the rest of the body covered with small ganoid scales. Pectorals long and wing-like, a scaly short tail. Twelve species; eight from the lower, and four from the Upper Devonian of Orkney, Cromarty, Caithness, Scotland, and in Ireland.
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Pteris
in botany, a genus of Polypodeæ. Sori continuous, linear, marginal; involucre scarious or membranous, confluent with the recurved margin of the frond. Known species 80, of worldwide distribution.
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Pterocarpus
in botany, a genus of Dalbergieæ, having a thin wing at the edge of the fruit. Large trees, chiefly from the tropics. P. marsupium, P. indicus, and P. macrocarpus furnish East Indian kino, and P. erinaceus, African kino, P. draco and P. santalinus, red sandal wood. P. balberggioides, a good Indian wood, and P. indicus, the excellent Andaman red wood. Cattle and goats feed on the leaves of P. marsupium.
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Pteroceras
in zoology, scorpion shell, or spider shell. Shell, when young, like that of Strombus; afterward the outer lip becomes prolonged into several long claws, one of them forming a posterior canal. Recent species 12, from India or China.
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Pteropoda
in zoölogy, a class of Cuvier's embranchement of sub-kingdom Mollusca. Also, a sub-class of Cephalopoda, in which the mid-region of the foot is drawn out into a pair of winglike muscular lobes, used as paddles. The hind region is often absorbed, but may carry an operculum; the fore region is sometimes drawn out into tentacles, provided with suckers. There are two orders: Thecosomata and Gymnosomata.
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Pterosauria
an order of flying Reptilia of Mesozoic age. No exoskele- PTOLEMÆUS ton trunk; dorsal - ribs vertebræ double - headed procœlous; broad, anterior sternum, with median keel, and ossified sternal ribs. Jaws generally armed teeth, implanted in distinct sockets with The fore - limb consists of a. ulna, and radius, carpus, and humerus hand of, trivance four fingers, the outer clawless the inner and three enormously unguiculate elon-, gated. Supported by this finger, the PTERODACTYLS side of the body, and the comparatively short hind limb, was a patagium, or flying membrane. The bones were pneumatic. PTOLEMÆUS, the dynastic name of 13 kings of Egypt, who reigned from 323 to 43 b. c. The most famous was Ptolemæus Soter, who reigned from 323 to 285 B. C. See PTOLEMY I.
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Ptolemaic System
the hypothesis maintained by Ptolemy in his "Almagest " that the earth was a fixed body, remaining constantly at rest in the center of the universe, with the sun and moon revolving round it as attendant satellites. To account for the more complicated movements of the planets, a conter planet of revolved was devised in a circle by, while which the each centhat circle described another circle round the earth. The Ptolemaic system prevailed till Copernicus propounded what is now accepted as the true system of the universe. See COPERNICUS;
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Ptolemies, The
tol'e-miz, The, a house of Grecian rulers of Egypt. The dynasty was founded by Ptolemy I, a celebrated Macedonian general who, in 323 B. C., took Egypt as his share of the Empire of Alexander the Great. He made Alexandria his capital, and assumed the title of king, 306 B. C. Ptolemy XII was the last of the name; Cleopatra, the last of the family. The dynasty colonized Alexandria with Greeks and made that city for a century or two the center of Greek learning and literature. Greek was thus made the official language of Egypt. See Alexandria ; Cleopatra ; Ptolemy
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Ptolemy
a celebrated astronomer. A native of Egypt. Dates are uncertain, but he is known to have flourished in Alexandria about 139 A. D. He wrote in Greek, the language of learning at that time. He was an eminent writer on geography and mathematics, but in many respects his teachings were far less scientific than the earlier ones they replaced. He is especially noted for his views of the movements of the sun, moon, and stars. According to Ptolemy, the earth is the center of the universe. The sun, moon, and stars are set in crystal globes which turn around the earth daily carrying the heavenly bodies around with them. This theory would be interesting merely as a curiosity, were it not that the so-called "Ptolemaic System" was adopted and held by the authorities of the church as in accordance with the Bible; for Joshua commanded the sun to stand still and it obeyed him. See Joshua x:12, 13, and Habakkuk iii:11. To doubt the Ptolemaic system was to doubt the Bible and scorn the teachings of the church. Ptolemy was an accepted authority until the middle of the fifteenth century. See Copernicus ; Galileo
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Ptolemy (CLAUDIUS a celebrated)
CLAUDIUS, a celebrated astronomer and geographer, who flourished at Alexandria, about A. D. 140-160. He is considered the first astronomer of antiquity. He corrected Hipparchus' catalogue of the fixed stars, and formed tables by which the motions of the sun, moon and planets might be calculated and regulated. He was the first who collected the scattered and detached observations made by the ancients, and digested them into a system; system; this he called the "Great Construction." (See PTOLEMAIC SYSTEM.) The " Great Construction " was translated by the Arabians into their language about 827, and from this translation, which bears the title of "Almagest," a Latin version, was made by command of the Emperor Frederick II., in 1230.
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Ptosis
in pathology, a falling; as Ptosis palpebræ, a paralysis of the muscle which should keep the upper eyelid from falling.
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Puberty
the age at which persons or bearing chilare capable of begetting dren; the period marked by the functional development of the generative system in both male and female, and their corresponding aptitude for pron. In botany, the period at which creation. a plant first begins to bear flowers.
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Pubilius Volero
the author of the Pubilian law at Rome; a law by which the power of the plebs or people was greatly increased.
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