The agamas have always two pairs of well-developed limbs. The teeth are usually differentiated into incisors, canines and molars. The skin is devoid of ossifications, but large and numerous cutaneous spines are often present, especially on the head and on the tail. The family, comprising some 200 species, with about 30 genera, shows great diversity of form; the terrestrial members are mostly flat-bodied, the arboreal more laterally compressed and often with a very long tail. Most of them are insectivorous, but a few are almost entirely vegetable feeders. They are an exclusively Old World family; they are most numerous in Australia (except New Zealand) and the Indian and Malay countries; comparatively few live in Africa (none in Madagascar) and in the countries from Asia Minor to India. The majority of the ground-agamas, and the most common species of the plains, deserts or rocky districts of Africa and Asia, belong to the genera _Stellio_ and _Agama_. Their scales are mixed with larger prominent spines, which in some species are particularly developed on the tail, and disposed in whorls. Nearly all travellers in the north of Africa mention the _Hardhón_ of the Arabs (_Agama stellio_), which is extremely common, and has drawn upon itself the hatred of the Mahommedans by its habit of nodding its head, which they interpret as a mockery of their own movements whilst engaged in prayer. In some of the Grecian islands they are still called _korkordilos_, just as they were in the time of Herodotus. _Uromastix_ is one of the largest of ground-agamas, and likewise found in Africa and Asia. The body is uniformly covered with granular scales, whilst the short, strong tail is armed with powerful spines disposed in whorls. The Indian species (_U. hardwicki_) is mainly herbivorous; the African _U. acanthinurus_ and _U. spinipes_, the Dab of the Arabs, take mixed food. _Phrynocephalus_ is typical of the steppes and deserts of Asia. _Ceratophora_ and _Lyriocephalus_ scutatus, the latter remarkable for its chameleon-like appearance, are Ceylonese. _Calotes_, peculiar to Indian countries, comprises many species, e.g. _C. ophiomachus_, generally known as the "bloodsucker" on account of the red colour on the head and neck displayed during excitement. _Draco_ (see DRAGON) is Indo-Malayan. _Physignathus_ is known from Australia to Cochin China.