THE TEETH OF KEPTILES 107 



the fifth or sixth tooth above. In old individuals 

 it sometimes happens that the lower teeth become 

 of such a length as to penetrate through the 

 upper jaw entirely and appear outside when the 

 mouth is closed. This also occurs in the Caimans 

 of South America, which are like the Alligators 

 in regard to their dentition. The G-avials of In- 

 dia have a remarkable snout, which is elongated, 

 narrowed from the cranium, and again enlarged 

 to a spoon-shape at the end. Owing to the extra 

 length of the jaw, it has more teeth than the 

 crocodiles, and they are of more uniform size. 

 The "canine" tooth fits into a notch on the side 

 of the muzzle like that of the crocodiles. The 

 extinct crocodiles were characterized by larger 

 and more numerous teeth, which sometimes had 

 longitudinal ridges upon the crowns. 



The Ophidia comprises the serpents of all kinds, 

 which are of well-known form, and have neither 

 limbs, scapula, thoracic or pelvic arches, — except 

 in the Boas, which have rudimentary pelvis and 

 hind limbs. The skin is covered with glittering 

 scales, which are smooth in the non-poisonous 

 species and keeled in the poisonous varieties. 

 The bones of the skull are loosely joined by elastic 

 ligaments. This provision enables the snakes to 

 open the mouth to a prodigious extent and to 

 protrude and retract the jaws, so as to inclose 

 and swallow prey as large or even larger than the 



