122 CALIFORNIA ACADEMY OF SCIENCES. 



Distribution. The Gila Monster has been found in 

 the Valley of the Virgin, about eight miles below Bunk- 

 erville, near the eastern boundary of Nevada. It may 

 be that it occurs on portions of the deserts of southeast- 

 ern California, but as yet no specimens from this area 

 have found their way into museums. 



Habits. The Gila Monsters are the only lizards whose 

 bite is known to be poisonous. TJie venom is secreted 

 by large glands situated just under the chin, and flows 

 out, onto the floor of the mouth, between the lips and 

 the gums. Being below the teeth and not directly com- 

 municated to them, the poison sometimes fails to find 

 its way into a wound although the teeth are grooved to 

 afford it a passage. The upper jaw of the Monster is 

 provided with a saliva which possesses no poisonous 

 properties. This harmless saliva appears to be present 

 in the lower jaw as well as the upper, but is there mixed 

 with venom about as deadly as that of the rattlesnakes. 

 Although provided with so powerful a poison, the Gila 

 Monster is so gentle and sluggish that it is not always 

 easy to cause one to bite, but when thoroughly angered 

 it bites fiercely, throwing its head to one side with 

 lightning-like quickness and holding like a bull-dog to 

 whatever it has seized. Sumichrast says that it turns 

 onto its back before biting. Although this observation 

 has not been confirmed, the presence of venom in, 

 the lower jaw only would explain such an action. In 

 spite of its clumsy form it sometimes climbs bushes, 

 probably in search of bird's eggs, which, together with 

 young rabbits, etc., form its food. 



Family VII. XANTUSIID^. 



This family contains but three genera; one Central 

 American, one West Indian, and one Californian. The 



