554 TEXTBOOK OF ZOOLOGY 



The other species, II. horridum, ranges through central and western 

 Mexico to northern Central America. These lizards may reach a 

 length of 2 feet though smaller ones are more commonly seen. The 

 surface of the body is totally unlike that of any other lizard, being 

 covered by beadlike ossicles or tubercles. The most interesting and 

 distinctive structural characteristic of these lizards is their grooved 

 teeth with ducts from poison glands opening at the base of the 

 grooves. No other family of lizards in America is venomous. The 

 color of H. suspectum is black marbled with pale pink, salmon, or 

 flesh. The Mexican species is black with yellow or lemon spots or 

 bars. The short thick tail becomes more slender when the animals 

 fast. The natural food of the animals is not known. They take 

 eggs readily in captivity and thrive on them. Reproduction is 

 oviparous, the eggs being laid in warm, moist sand where they 

 hatch in twenty-eight to thirty days. 



Family Xantusiidae (night lizards). — This small family contains 

 only three genera with a total of seven species. Five species, all 

 of the genus Xantusiidae, are found in southern California, Lower 

 California, and Arizona. One other genus is found in Central 

 America ; and a third in Cuba. 



These lizards are seldom over six inches in length. The color 

 changes from dark brown in subdued light to lighter hues in 

 stronger light. The pupils are vertical, and the eyes are without 

 lids. The tongue is only slightly extensible. 



These little reptiles are strictly nocturnal, hiding by day under 

 fallen Yucca plants or in crevices between boulders. So far as is 

 known they are insectivorous in feeding habits. At least one species 

 is known to be ovoviviparous. 



Family Teiidae (striped lizards, race runners, sand lizards). — This 

 family contains 40 genera with more than a hundred species. Twenty- 

 two species and subspecies, all belonging to the genus Cnemidophorus, 

 are found in the warmer parts of the United States. All other 

 members of the family are found in South America and the West 

 Indies. 



The species of Cnemidophorus are long slender, active lizards cap- 

 able of surprising speed in running. The ground color is usually 

 some shade of brown. Lines, bands, or spots of lighter color form 

 various patterns on different species. The tongue is black, forked, 

 and protractile. 



