378 
VERTEBRATA. 
and is found in Mexico, Avliere it is considered venomous, thougli this is an error. It is the otily 
animal of this family found in America. Dr. Gray arranges it in a separate family, to which he 
gives the name of Helodermidce. 
There are other species of Varanidse in Europe, Asia, Africa, and Australia, which frequent 
dry and sandy places. The Psammosaurus scincus is found in the deserts of Egypt, and is sup- 
posed to be the skink of the ancients. 
THE WALL GECKO. 
THE GEOKOTID-/E. 
These, as well as the succeeding families are called Thick-iongued Lizards. Of the present 
group there are a great many species, distributed in various parts of the world. They have the 
eyes large and the legs short and terminated by five nearly equal toes ; these are destitute 
of claws, but they are furnished beneath with a peculiar apparatus for clinging, very similar in 
its action to that by which many insects are enabled to walk upon polished perpendicular sur- 
faces. Tlie lower part of each toe is dilated, forming a sort of disc, the inferior surface of which 
is composed of numerous transverse, notched laminae, between which a sticky fluid exudes. By 
means of this apparatus the Geckos are enabled to run up a perpendicular wall with great facility, 
and even to cross a ceiling with their, backs downward, a power which, no doubt, assists them 
greatly in the capture of the flies and other insects which constitute their principal food. They 
are nocturnal animals, and very active, moving about with great rapidity, but without the least 
sound. They are very abundant in warm climates, especially in Southern Asia. They are gener- 
ally of a repulsive appearance, and this is no doubt the reason why many of the species are con- 
- sidered venomous, though erroneously so, by the inhabitants of the countries where they are found. 
Genus PLATYDACTYLUS : F lahjdact^lus. —Th\& includes the Wall Gecko, P. muralis— 
one of the species known in the south of Europe, and inhabiting all the countries bordering on 
the Mediterranean. It is about six mches long, and receives its specific name from living in 
the walls of old buildings. Tlie term Gecko is said to be derived from the note of one of the 
species. 
Genus THECADACTYLUS : Thecadactylus.—Thx^ includes the Croaking Lizard of the 
West Indies, T. loevis, which frequents the sugar-boiling houses, reposing during the day upon 
the rafters. It is generally considered venomous, but this is undoubtedly a result of its repulsive 
appearance. 
