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134: HYLAS HYPERBOLA derm-like feet, and sacrum of five united verte- bra). It attained a size of 20 to 25 ft., and was believed by Mantcll and Buckland to have had an enormous dorsal dermal fringe like the Hylteosaurus. horny spines on the back of the iguana ; its skin was covered with circular or elliptical plates. 1IYLAS, in Greek mythology, son of Theoda- mas, king of the Dryopes, and the nymph Me- nodice. Hercules, after slaying Theodamas, adopted Hylas, and took him on the Argonau- tic expedition. When they arrived at Mysia, Hylas went to a neighboring well for water, but the maids of that fountain became so fas- cinated with his beauty that they drew him into the water, and he was never seen again. When Hercules shouted for him, the youth's voice was heard from the well like a faint echo ; and he was so enraged at his loss that he threatened to ravage the country of the My- sians if they did not produce Ilylas dead or alive. They sought him in vain, and ultimate- ly instituted an annual festival, during which they roamed over the mountains calling ont the name of Hylas. 1IYMKY, in Greek mythology, the god of mar- riage. According to some, he was a son of Apollo and one of the muses; but according to others, he was originally a mortal, who, having rescued some Attic maidens from Pe- lasgic pirates or other robbers, had his praises celebrated in token of gratitude in their bridal songs, which after him were called hymeneal songs. The practice of singing such songs at the nuptial season became in time universal, and the heroic youth was gradually elevated to the rank of a divinity. Hymen is represented in works of art as a tall handsome youth, car- rying in his right hand a bridal torch. IIYMENOPTERA (Gr. v/tijv, membrane, and KTep6v, wing), a suborder of insects, so named from their four membranous, transparent wings. They have upper horny jaws for biting, and softer and longer lower jaws with the tip adapted for collecting honey ; the females and neuters have a sting or piercer. All undergo complete metamorphosis ; the larva) of the stingers are soft, without legs, resembling maggots ; most of the larval piercers resemble grubs and caterpillars. They are diurnal, swift fliers, and surpass all other insects in the num- ber and variety of their instincts ; of the very numerous species none are aquatic. They in- clude the bees, wasps, ants, ichneumon flies, saw flies, &c., which are described under their respective titles. HYMETTUS, a mountain range of Attica, form- ing the S. E. boundary of the Athenian plain. It consists of two summits, the northern or greater Ilymettus, the apex of which is about 3,500 ft. above the sea, and the southern or lesser Ilymettus, denominated Anhydrus, "the waterless," by the ancients. The honey of Ilymettus was considered by the ancient Greeks as inferior only to that of Hybla in Sicily ; but at present, though still abundant, it is said to be of very poor quality. The excellence of its marble is a favorite theme with classic authors. The greater Ilymettus is now called Trelo-Vuno, and the lesser Mavro-Vuno. HYOSCYAMS. See HENBANE. HYPATIA, a Neo-Platonic philosopher, born in Alexandria about 370, killed in 415. She was the daughter of Theon, a distinguished mathematician and astronomer. She went to Athens near the close of the 4th century, and studied under the Neo-Platonist Plutarch, who expounded to a small circle of disciples the Chaldean oracles and the secrets of theurgy. On her return to Alexandria, her talents, beau- ty, eloquence, and modesty made her an object of admiration. She revived the school of Ploti- nus, and became its head. But both as a pa- gan and as a philosopher she provoked the hos- tility of Cyril, bishop of Alexandria. Not only was her lecture room thronged, but she was consulted by the most considerable persons of the city, among others by the prefect Orestes, who was at constant feud with the bishop. The city was a prey to the violence of parties, and it was to the influence of Hypatia that Cy- ril attributed the refusal of Orestes to come to a reconciliation. " Certain persons, therefore," says the ecclesiastical historian Socrates, " of fierce and over-hot minds, who were headed by one Peter, a reader, conspired against the woman, and observed her returning home from some place ; and having pulled her out of her chariot, they dragged her to the church named Csesareum, where they stripped her and mur- dered her. And when they had torn her piece- meal, they carried all her members to a place called Cinaron, and consumed them with fire." Hypatia was the author of two mathematical treatises, which are lost, and there remains from her only an astronomical table inserted in the manual tables of Theon. She is the heroine of Charles Kingsley's " Hypatia." HYPERBOLA (Gr. imeppdMitw, to transcend), one of the conic sections, produced when the cutting plane makes a smaller angle with the axis of a right cone than is made by the side. The shadow of a globe on a flat wall, when part of the globe is further than the luminous point is from the wall, gives a hyperbola. Hy- perboloids are surfaces generated by moving hyperbolas.