GILA MONSTER (Heloderma suspectum), the only lizard known to be poisonous. It inhabits deserts in the south-western United States, chiefly in the valley of the Gila river in Arizona and New Mexico. The Gila monster is usually about 2 ft. in length and has a thick body covered with small bead-like tubercles. In colour it is blackish or purplish, with large, some what transverse, pinkish or yellowish blotches. The poison fangs are in the lower jaw, and its bite has been known to cause death in man. This lizard is usually sluggish but, especially in the wild state, is vicious when aroused, snapping its powerful jaws from side to side with an unexpected agility, all the while emitting sharp hisses. Its grip is very tenacious and cannot be broken by man without some prying instrument. In movement the Gila Monster is slow and methodical, but not clumsy, dragging rather than lifting its body over the ground. It is oviparous, depositing its soft-shelled eggs in the sand. (See LIZARD, REPTILES.)