Page:The Osteology of the Reptiles.pdf/286

268 "Gila Monsters" of Arizona. They are thickset, slow lizards with a club-like tail, reaching a length of about two feet, the only known poisonous members of the suborder.

Eocene. Glyptosaurus Marsh, Thinosaurus Marsh, North America. Placosaurus Gervais, France.

Oligocene. Helodermatoides Douglass, North America.

. Quadrupedal, terrestrial lizards. Upper surface of skull with numerous dermal bones. Temporal opening roofed over by the postfrontal extending back between parietal and squamosal, the arches complete. A parietal foramen. Teeth pleurodont.

The family of Lacertidae comprises about one hundred species restricted in distribution to Europe, Asia, and Africa. None is large and some are common throughout England; one, Lacerta vivipara, is the only reptile known to occur in Ireland.

Miocene. Lacerta, France.

. Arboreal, terrestrial, or subaquatic lizards attaining a length of three feet. No postorbito-squamosal arch. A parietal foramen. No dermal ossicles. Zygosphenes sometimes present.

A family of American lizards including about one hundred species, some, like the Cnemidophorus, common throughout the United States. The teeth of Dracaena are large oval, crushing organs.

Uppermost Cretaceous. ? Chamops Marsh, North America. Oligocene, Tejus.

. Temporal arch complete. Temporal openings roofed over by dermal bones. Body also covered by dermal ossicles beneath the corneous scales. Quadrupedal, bipedal, or limbless; terrestrial, subaquatic, or burrowing. Pleurodont.

The large family of skinks comprises about four hundred living species, cosmopolitan in its distribution. Some attain a length of about two feet. Trachysaurus of Australia is peculiar in its stumpy tail and very large scales of the body. Cyclodus has spherical crushing teeth.

Lower Cretaceous (Neocomian). Ardeosaurus Meyer.

Eocene. Cadurcosaurus Filhol, France.