IGUANA, amid MOSOSAIIRECS, ante.
Order 4, Crocotillia.—This is the highest order of living reptiles, and includes the crocodiles (q.v.), alligators (q.v.). and gavials (q.v.). See also JACARE and CAYMAN. • Extin,et Orders of Reptiles.—Order 5, Ichthyopterygia, Owen (Ichthyosauria, See IcumvosAuitus, ante.
Order 6, Sauropterygia, Owen (Piesiosauria, Huxley). See PLESIOSAURUS, ante.
Order 7, Anorrwdontia, Owen (Dicpwdontia, Huxley). The prominent characters of this order arc in the jaws, which are regarded as having been encased in horn, forming a kind of beak like that of chelonians. In the genus oudenodon, both jaws were probably without teeth, but in the other genus, dicynodon, the upper jaw was furnished with two long tusks. The pectoral and pelvic arches were very strong, and the limbs well devel oped and adapted to walking and not swimming. These forms are found in the triassic strata of s. Africa and India.
Order 8, Pterosauria.—This order includes the extraordinary group of flying reptiles belonging to the mesozoic epoch. Sec PTERODACTYL, ante.
Order 9, Dinosauria.—Most of these animals were gigantic, and supposed by some to have had affinities with the pachydermatous mammals. The skin was sometimes naked,
sometimes having an exo-skeleton of bony shields like those of crocodiles; anterior trunk-ribs double-headed; teeth set in distinct sockets. There were always two pairs of limbs, very strong and furnished with claws. In some the fore limbs were small com. pared to the hinelimbs. See DINOSAURIA, ante, HADROSAURUS, HYL2E0SAIIRLIS, IGUAN ODON, MEGALOSA.17RUS, and TITANOSAIIRIIS.
Order 10, Theriodontia.—This order was established by prof. Owen for the reception of a number of carnivorous reptiles of the triassic period. The dentition is of the car nivorous type, there being three distinct sets of teeth, incisors, canines, and molars. The canines were long and pointed. In cynodraco, which is regarded as the typical genus, the canines are not only immense, but are compressed, and have the hinder trenchant border minutely serrated, as in the caiaines of the saber-toothed tiger or machterodus .(q.v.). The humerus also resembles in some respects that of the cat family, and other carnivorous mammals, in having a supra-condyloid foramen for the protection of the median nerve and brachial artery.