XII INTRODUCTION. 



in two opposable groups. Such an arrangement of the toes, with the pre j 

 hensile tail, enables the animals to walk lengthwise of the small branches 

 with readiness. They spend their lives in the trees, and feed mainly upon 

 insects, capturing them with the tongue, which can be thrust forward several 

 inches for the purpose. The females lay from eight to a dozen eggs under 

 the fallen leaves. In this group the transient variations of color are exces- 

 sive in amount and rapidity; they often differ on opposite sides. Ability 

 to take on at will the color of any object upon which an individual may be 

 placed does not exist. 



Most of the Gecconidce have rudimentary eyelids, and the eyeball covered 

 \>j a transparent membrane under which it moves with freedom. A few 

 have connivent lids. The pupil is most often oblong and erect. The tongue 

 is short and thick. The skin is covered with granular or tubercular promi- 

 nences, which are not imbricated. In the greater number of the sj)ecies the 

 feet are provided with adhesive apparatus under the toes in the shape of 

 expansions or transverse series of plates, with which they are able to cling 

 to vertical and smooth surfaces. These disks vary greatly in the different 

 genera. Sometimes there are no disks, and sometimes the claws are absent. 

 Occasionally the claws are retractile as in cats. The body and head are 

 commonly depressed. When broken or lost, the tail grows out again; it 

 may be reproduced a number of times in the life of the individual. This 

 organ takes on fantastic shapes in some species; in all it is very fragile. 

 Ptychozoon is marked by fringed dermal expansions on sides of tail, body, 

 and head, which form a sort of parachute, answering a similar purpose 

 when leaping to that of the membranes of Draco. The name Gecco is given 

 in imitation of the voice. Geccoes live in the tropics of both hemispheres. 

 Some frequent houses, where they are very useful on account of their insec- 

 tivorous habits. In the United States a single species is represented, 

 Sjjhaeriodactylus notatus Bel., at Key West, Florida. Three or four others, 

 belonging to Coleonyx, Diplodactylus and Phyllodactylus, are reported from 

 Sonora and Lower California. Farther South they are more common. 



The Agamidce belong to the Eastern Hemisphere. In this family the 

 eye and eyelid are well developed, the teeth are generally planted ujjon the 

 upper edges of the bones of the jaws, the tongue is thick, and slightly, or 

 not at all, extensile, the scales are imbricate, and the tail not nearly so 

 fragile as in other Saurians. The toes are without disks. Of the odd forms 

 in the various subfamilies, probably none is more striking than that of the 



