386 ANATOMY OF VERTEBRATES. 



With respect to number, in no existing Reptile are the teeth 

 reduced so low as in certain Mammals and Fishes ; nor, on the 

 other hand, are they ever so multiplied as in many of the latter 

 class. Myohatrachus paradoxus, an Australian Frog, has but two 

 teeth in the premaxillary bones. The extinct Dicynodont Reptiles 

 of South Africa had two long tusks implanted in the upper jaw, 

 fig. 271.' Some species of Amphisbana {A. alba), with fifteen 

 teeth in the upper jaw and fourteen in the lower jaw, and certain 

 Monitors ( Varanus), with sixteen teeth in the upper and fourteen 

 in the lower jaw exemplify a low number of teeth amongst 

 existing Reptiles ; and certain Batrachians, with teeth ' en cardes ' 

 at the roof of the mouth, or which have ujDwards of eighty teeth 

 in each latei'al maxillary series, present the opposite extreme. 

 Rarely, however, is the number of the teeth so fixed and 

 determinate in any Reptile as to be characteristic of the 

 si^ecies, and still more rarely have the individual teeth such cha- 

 racters as to be determined homologically from one species to 

 another. 



With respect to situation, the teeth may be present on the jaws 

 only, i. e. the maxillary, the premaxillary, and mandibular bones, 

 as in tlie Crocodiles, fig. 95, and many Lizards : or upon the jaws 

 and roof of the mouth : and here either upon the pterygoid bones, 

 as in the Iguana, fig. 98, D, 24, and Mosasaur; or upon both 

 palatine and jiterygoid bones, as in most Serpents, fig. 266, 20, 24; 

 or upon the vomer, as in most Batrachians, fig. 265, I; or upon both 

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

 vomerine and sphenoid bones, as in Salamandra glutinosa. With 

 respect to the marginal or jaw teeth, these may be absent in the 

 premaxillary bones, as in many Serpents, fig. 266, 22 : or they 

 may bo present in the upper and not in the lower jaw, as in most 

 Frogs: or in both upper and lower jaws, as in the tailed 

 Batrachians : and among these they may be supported, upon the 

 lower jaw, by the prcmandibular or dentary piece, as in the 

 Salamanders, Menopome, Amphiume, Proteus : or upon the 

 splcnial piece, as in the Siren: or upon both splcnial and pre- 

 mandibular 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 splcnial teeth 

 are always so arranged in the few species that possess them. The 

 intermaxillary, maxillary, and prcmandibular teeth are uniscrial, 

 or in one row, with the exception of the Crecilia and the extinct 



' ci.viii. vo). vii. ]i, 59. 



