THE TEETH OF KEPTXLES 105 



closed, as with most reptiles. The teeth are 

 rounded, conical, more or less compressed or oval 

 in section, and rather blunt. The mandible and 

 maxillary are long, the condyle of the mandible 

 is hollowed and fit over a tuberosity on the tem- 

 poral bone, being the reverse to what it is in the 

 mammals. The teeth are much reduced from the 

 long, cone shape of fishes and vary much in shape ; 

 some are long, curved, and acute; others are 

 short and obtuse, and others have a flat, sharp 

 edge which may be serrated. The forms are very 

 erratic, even in the same species. They are com- 

 posed of fine, hard dentin, covered with cemen- 

 tum and with enamel in some species, usually a 

 thin layer confined to the point. The teeth are 

 implanted in sockets which are formed by septi 

 crossing the dental groove, which is open and 

 continuous in most of the lizards. New succes- 

 sional teeth are being constantly developed be- 

 neath or at the sides of the old ones. As a new 

 tooth erupts it presses against the base of the 

 old one, causing its absorption, and, pushing it 

 upward, carries it like a cap on its apex until it 

 is lost. The successional teeth follow each other 

 and become "nested" one with the other. In the 

 Crocodiles proper the teeth are set on the margin 

 of the jaw in distinct sockets, and are long, coni- 

 cal, somewhat pointed, and compressed to form 

 sharp edges. The teeth vary much in size and 



