58 INTRODUCTION 



groove ; and the Proteroglyphs, in which grooved or 

 canaliculated teeth are situated in front, followed or 

 not by solid teeth. Beyond these three principal 

 divisions, the dentition furnishes important characters 

 for the classification, although that importance has 

 sometimes been over-estimated. The maxillary teeth 

 may be equal in length (Isodonts), or the anterior the 

 longer (Lycodonts), or the posterior the longer, in- 

 creasing gradually in size (Coryphodonts) or abruptly, 

 without (Syncranterians) or with a diastema, or break, 

 in front of them (Diacranterians). These categories 

 are, however, so completely connected as to preclude 

 their use in taxonomy beyond helping to define 

 genera. The number of maxillary teeth and the 

 relative proportions and disposition of the mandib- 

 ular teeth also afford useful generic characters. 



The European genera may be arranged as follows, 

 according to the dentition : 



I. Teeth few, disposed in a transverse series in the 

 upper jaw only Typhlops. 



II. Teeth in both jaws and on the palatines and 

 pterygoids. 

 A . A series of solid teeth along the maxillary ; no 

 grooved teeth. 

 t. Anterior maxillary and mandibular teeth 



longest; 9 or 10 maxillary teeth Eryx. 



2. Maxillary teeth equal, or increasing in size 

 posteriorly. 



