REPTILIA. 81 



GENUS III. ALLIGATOR, Cuv. 



The fourth tooth of the under jaw entering into a hole in 

 the upper ; toes of posterior limbs semi-palmated. [America 

 only.] 



FAMILY II. LACERTINIDA. 



Tongue extensible and terminated in two threads; five 

 free toes on each foot, unequal and armed with nails ; scales 

 of the abdomen and top of the tail arranged in transverse 

 bands. Two remarkable genera. 



GENUS I. MONITOR. 



Large size ; tail flattened laterally ; teeth to the jaws, not 

 to the palate. 



GENUS II. ' LACERTA. Lizard proper. 



Extremity of the palate armed with two rows of teeth ; a 

 collar under the neck formed of large scales ; a casque formed 

 by the projection of the cranium over the orbits. 



FAMILY III. IGUANIDA. 



All the characteristics of the second family except that the 

 tongue is not extensible. Two remarkable genera. 



GENUS I. AGAMA, Daud. 



Head enlarged behind ; no teeth in the palate ; scales of 

 the tail imbricate; spines on different parts of the body, 

 especially near the ear ; skin of the throat loose and suscep- 

 tible of inflation ; some have femoral pores, others none. 



GENUS II. DRACO, Lin. Dragon. 



No teeth in the palate ; the six first false ribs, instead of 

 investing the abdomen, extend in a straight line and support 

 a fold of the skin of the sides, forming a parachute ; scales 

 imbricate. 



GENUS III. IGUANA, Cuv. 



Teeth on the palate ; ribs formed in the ordinary manner ; 

 a range of recurved scales all along the back ; a dewlap under 

 the throat. [America.] 



