DIVISIONS OF REPTILIA, EN, 
species is the Blue-tailed Lizard (Sczucus fasciatus) of the United 
States. 
The Geckos (Geckotide@) form a large group of night-loving 
Lizards, which are found in most parts of the world, and chiefly 
deserve notice from the fact that their eyes are not provided 
with movable eyelids. ‘The Chameleons, also, cannot be said 
to possess movable eyelids, for the eye is covered with a single 
lid, leaving only a central aperture for the pupil. The common 
species (Chameleo Africanus) occurs abundantly in the north 
of Africa, and has long been known for the changes of colour 
which it has the power of exhibiting. It is a sluggish animal, | 
and catches insects by darting out its long and Brotrusible 
tongue with extreme rapidity. 
ORDER IV, CROCODILIA.—The last and highest order of the 
living Reptiles is that of the Cvocodzlia, comprising the Croco- 
diles, Alligators, and Gavials, and characterised by the follow- 
ing peculiarities : The outer or integumentary skeleton consists 
partly of horny scales developed by the outer layer of the skin, — 
and partly of large bony plates produced by the inner layer of 
the skin, The bones of the skull and face are firmly united, 
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Fig. 146.—Skull of young Crocodilus biporcatus (after Van der Hoven). 
and the two halves of the lower jaw are joined by a distinct 
suture. The teeth form a single row in both jaws, and are im- 
planted in distinct and separate sockets. The front ribs of the 
trunk are double-headed, and there are no collar-bones, The 
heart consists of four distinct chambers, two auricles and two 
ventricles, all completely separated from one another. The 
mixture of arterial and venous blood, however, which is so 
characteristic of Reptiles, is provided for by a communication 
between the great vessels which spring from the two ventricles 
in the immediate neighbourhood of the heart. The eyes are 
