The so-called colubrine venomous snakes, which retain in a great measure an external resemblance to the innocuous snakes, have the maxillary bone not at all, or but little, shortened, armed in front with a fixed, erect fang, which is provided with a deep groove or canal for the conveyance of the poison, the fluid being secreted by a special poison-gland.
In the other venomous snakes (viperines and crotalines) the maxillary bone is very short, and is armed with a single very long curved fang with a canal and aperture at each end.
The facial portion of the skull is very short; a long process of the maxillary bone descends from the anterior part of the zygomatic arch; and the ascending ramus of the mandible is remarkably high.
