180 NUMBER. SITUATION. 



holding, but not for dividing or masticating their food. The Siren 

 alone combines true teeth with a horny maxillary trenchant sheath 

 like that of the Chelonian reptiles. 



68. Number. — In no reptile are the teeth reduced to so small a 

 number as in certain mammals and fishes, nor are they ever so 

 numerous as in many of the latter class. Some species of Monitor 

 {Varanus) with sixteen teeth in the upper and fourteen in the low^er 

 jaw, afford examples of the smallest number in the present class, and 

 certain Batrachians, with teeth * en cardes' at the roof of the mouth, 

 or which have upwards of eighty teeth in each lateral maxillary 

 series, present the largest number. It is rarely that the number of 

 teeth is fixed and determinate in any reptile so as to be characteristic 

 of the species. 



69. Situation. — The teeth may be present on the jaws only, as 

 in the Crocodiles and many Lizards ; or upon the jaws, and roof of 

 the mouth, and here either upon the pterygoid bones as in the 

 Iguana and Mosasaur, or upon both palatine and pterygoid bones 

 as in most serpents, or upon the vomer as in most Batrachia, or 

 upon both vomerine and pterygoid bones, as in the Axolotl, or 

 upon the vomerine and sphenoid bones, as in the Salamandra gluti- 

 nosa, Maclure. With respect to the marginal or jaw- teeth, these 

 may be absent in the intermaxillary bones, as in many serpents ; 

 or they may be present in the upper and not on the lower jaw, as in 

 most frogs ; or in both upper and lower jaws, as in the tailed Batra- 

 chians ; and among these they may be supported, upon the lower jaw, 

 by the premandibular or dentary piece as in the Salamanders, Meno- 

 pome, Amphiume, Proteus ; or upon the opercular piece, as in the 

 Siren ; or upon both opercular and premandibular bones as in the 

 Axolotl. The palatine and pterygoid teeth may, in the Batrachians, 

 be arranged in several rows, like the * dents en cardes' of fishes : the 

 sphenoid and opercular teeth are always so arranged in the few 

 species that possess them ; the intermaxillary, maxillary and pre- 

 mandibular teeth are serial or in one row, with the exception of the 

 Caecilia and the extinct Labyrinthodon, which have a double row of 

 teeth at the anterior part of the lower jaw. 



70. Form. — The teeth of reptiles, with few exceptions, present a 



