326 REPTILIA 



with small reserve fangs at its base. This is moved to a vertical 

 position when a snake opens its mouth to strike its prey. In the 

 Chelonia there are no teeth but the horny jaws resemble a bird's 

 beak. The Crocodilia have many conical hollow teeth on the pre- 

 maxillae, maxillae and dentary. 



The tongues of certain Lizards are forked and retractile as in 

 Snakes. The chameleon has an extremely long club-shaped tongue. 

 In Snakes the tongue is extremely slender and is utilized as a tactile 

 organ. Some hold that it is sensitive to sound vibrations. 



In the esophagus of turtles there are large horny recurved papil- 

 lae. Crocodilia and Chelonia have a gizzard-like stomach. In 

 Lizards and Snakes a rudimentary cecum is found at the anterior 

 end of the large intestine. 



Respiratory System. — In the Snakes and some snake-like Lizards 

 there is a great reduction in the size of the left lung. Chameleons 

 have inflatable air-sacs which enable them to puff up and startle 

 their enemies. The Crocodilia and Chelonia have large and well- 

 developed lungs. 



In the Crocodilia the nostrils are at the upper end of the snout 

 and can be closed by two valves. In front of the choanae, two soft 

 " palatal folds " shut off the mouth from the pharynx. When a 

 crocodilian is drowning its prey, it can push the glottis anteriorly to 

 meet the posterior nares, and then respire comfortably. 



Old ma.\e gavials have a cartilaginous hump containing air which, 

 situated at the tip of the snout, enables them to remain under water 

 longer than younger animals. 



Superficial Differences between the Crocodilia 



Alligator. Crocodile. 



Exposes four points above water Exposes snout and neck crest when 



when floating — the eyes and the floating, 

 nostrils. 



Fourth tooth from front bites into Fourth lower tooth from front pro- 

 socket in upper jaw; in older ani- jects slightly outward and fits in- 

 mals it may pierce jaw and show to grooved notch in outer edge of 

 from above. upper jaw. 



Makes nest of sticks and grass. Makes nest in sand. 



Less active and vicious. More active and vicious. 



The caimans may have a blunt snout like the alligator or a 

 pointed one like the crocodile. They also have the fourth tooth of 



