552 TEXTBOOK OP ZOOLOGY 



tion in size, form, and coloration occurs. The chameleons (Anolis) 

 change from various shades of brown to light green in response to 

 changes in the intensity of the light. Members of the Central Ameri- 

 can genus Basiliscus are remarkable for erectile middorsal crests. The 

 horned lizards (Phrynosoma) bear conspicuous osseous spines or 

 "horns" on the posterior and lateral borders of the head. All the 

 members of the family, however, have certain structural character- 

 istics in common ; such as, fleshy tongue, and eyes with round pupils 

 and well-developed lids. Femoral pores are usually present on the 

 males. Most of the species found in the United States lay eggs, 

 though some species are known to be ovoviviparous. Various types 

 of habitats have been adopted by different iguanid lizards. The 

 chameleons and many species of the genus Sceloporus are essentially 

 arboreal, while the homed lizards (Phrynosoma) are strictly ter- 

 restrial. 



Crotaphytus collaris, the collared lizard, is a rather large lizard with 

 a long tail and a heavy body. It is brightly colored and has a yellow 

 collar bordered with black. Its distribution is in the Southwest, 

 from the Plains westward. 



Certain tropical species are semiaquatic and one species is semi- 

 marine. The majority of species are insectivorous, though three 

 genera are herbivorous. 



Family Anguidae (Alligator lizards, "glass snake," joint snake, 

 etc.). — This interesting group of lizards is represented in the United 

 States by 10 species. Approximately 40 other species are found in 

 other regions of the world. Most of these other species are native 

 to the tropical regions of the Western Hemisphere, though some are 

 found in Europe, Asia, and Africa. A reduction in the size and 

 strength of the limbs is common in this family. Many species, such 

 as our "glass snake," are entirely legless. Other common charac- 

 teristics are a fold in the skin where the ventral plates join the 

 body wall ; a long, brittle tail ; eye with a lid ; emarginate, protractile 

 tongue; and solid teeth. Many of our species have large auditory 

 openings connected by an unobstructed passage. Our largest species 

 reaches a maximum length of approximately one foot, while a form 

 found on the Balkan peninsula may be three feet long. Our alliga- 

 tor lizards (Gerrhonotus) are ovoviviparous while the "glass snake" 

 (Ophisaurus) lays eggs. All members of this family feed on animal 

 food, such as insects, snails, and small mammals. 



