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Rh Uppermost Cretaceous. ? Coniophis Marsh, North America.

Eocene. ? Helagras Cope, North America.

Oligocene. Neurodromicus Cope, North America.

Miocene. Vipera Laurenti, Germany.

Pleistocene. Crotalus Linné, North America.

. Ectopterygoids present. Maxillae horizontal, not erectile, their anterior teeth deeply grooved or hollowed. Caudal hypophyses bifid. Laophis, Salonica.

This family of highly poisonous snakes, in its wider sense including the cobras, sea snakes, and the coral snakes of the southern United States, comprises nearly two hundred living species. They are practically unknown as fossils. Cobras (Naja Laurenti) have been reported from the Pleistocene of France, but doubtfully.

. Ectopterygoid present, the coronoid absent. Maxillae horizontal, with solid teeth. Tabular present. Postorbital not produced forward.

This family of harmless snakes includes more than half of all living species, none attaining a size of more than seven or eight feet. Their distribution is world-wide.

Miocene. Elaphis Aldrich, Tamnophis Rochebrune, Pylemophis Rochebrune, Periops Wagler, Europe.

Pleistocene. Coluber Linné, Europe and North America [ = ] Bascanion Baird and Gerard, North America.