TEETH OF EEPTILES. 



399 



inferior surface, as it lies horizontally, with the apex directed 

 backward ; the capsule adheres to this inflected surface of the 

 pulp ; and the base of the groove of the loose growing poison- 

 fano; is brought into the same relation with the duct of the 



o o 



poison gland as the displaced fang, which has been severed from 

 the duct. 



The existing species of Lizards differ from those of Crocodiles 

 in the anchylosed condition of the teeth, which present few modi- 

 fications of importance : those that yield most fruit to physiology, 

 and which have most expanded our ideas of the extent of the 



271 



Skull of Dicynodon lacerticeps, one third natural size 



resources of Nature and the exceptional deviations from what 

 was deemed the rule of structure in the Saurian dentition, 

 have been discovered by the study of the fossil teeth of extinct 

 forms of the order. Amongst these the most extraordinary are 

 those called e Dicynodonts,' 1 from their dentition being reduced 

 to one long and large canine tooth on each side of the upper 

 jaw. These teeth recall, at first sight, the character which the 

 long poison-fangs give, when erected, to the upper jaw of 

 the Rattle snake. The alveolar border of the lower jaw and of 

 the premaxillary part of the upper jaw is trenchant, and seems 

 to have been sheathed with horn. The maxillary, fig. 271, 

 21, is excavated by a wide and deep alveolus, with a circular 

 area, and lodges a long and strong, slightly curved, and sharp- 

 pointed tusk, which projects about two thirds of its length from 



1 From Sis, two, and Kvv6Sous, the name given by Hippocrates to the canine teeth, 

 and signifying the same idea as their common English denomination. 



