INTRODUCTION. XIX 



with which all the species are covered, we have happily no indi- 

 genous example, nor would any of them bear the cold of our 

 climate. The Crocodiles and Alligators of both worlds, and 

 the Gavials of India, constitute this order. They are dis- 

 tinguished from the true Saurians, or Lizard tribe, by several 

 important characters. Of these, the most tangible and ob- 

 vious is that upon which the name of the order is founded ; 

 the covering of the whole of the back part of the neck, 

 body, and tail, with distinct series of bones, of moderate size, 

 embedded, as it were, in the substance of the skin, and 

 covered externally with a thick cuticle. These dermal bones 

 are usually furnished with a crest, which renders them ex- 

 ceedingly strong, and they altogether form a panoply of de- 

 fence which can resist the attacks of the most powerful 

 enemies of whatever kind. These animals are carnivorous, 

 taking their prey generally in the water, but retiring to the 

 shore to devour it, which they often defer until it has become 

 half putrid. For the reasons given above, I do not think it 

 necessary to enter into particulars respecting the structure and 

 history of these animals. They can never become of local 

 interest to us, as they are not made subservient to any pur- 

 pose of utility to man, nor can they be naturalized in our 

 latitude. 



The true Saurians are characterized by the existence of 

 both anterior and posterior extremities, and of a moderate 

 number of perfect and moveable ribs, by an entire covering of 

 scales, which in most families are imbricated, in others flat 

 and with their margins in mutual contact. The eyes are fur- 

 nished with eyelids ; the ear in some protected by a simple 

 valve, in others by scales rather larger than the surrounding 

 ones, and in others the tympanum is on a level with the sur- 

 face of the skin. 



In this group are found some of the most active, and cer- 

 tainly the most beautiful of the reptile class. Many of them 



