TEETH OF EEPTILES. 393 



Tlie Labyrintliodon combines both these dispositions of the joalatal 

 teeth. The lower jaw, like the upper, contains a series of small 

 teeth, with a few larger tusks anterior to them. The sockets of 

 the teeth are shallower than in the upper jaw ; the outer wall is 

 more developed than the inner, and the anchylosed bases of the 

 teeth more nearly resemble, in then- oblique position, those of 

 existing Batrachia. Between the apex and the part where the 

 inflected vertical iblds of the cement commence, the tooth of the 

 Labyrinthodon resembles, in the simplicity of its intimate struc- 

 ture, that of the entire tooth of ordinary Batrachia and most 

 reptiles ; and in the lower or basal half of the tooth the lal^yrinthic 

 structure above described commences, and gradually increases in 

 complexity. 



In the genus Deirodon,^ the teeth of the ordinary bones of the 

 mouth are so small as to be scarcely perceptible ; and they appear 

 to be soon lost. An acquaintance with the habits and food of this 

 species has shown how admirably this apparent defect is adapted 

 to its well-being. Its business is to restrain the undue increase of 

 the smaller birds by devouring their eggs. Now if the teeth had 

 existed of the ordinary form and proportions in the maxillary and 

 palatal regions, the egg would have been broken as soon as it was 

 seized, and much of the nutritious contents would have escaped 

 from the lipless mouth of the snake in the act of deglutition ; Ijut, 

 owing to the almost edentulous state of the jaws, the egg glides 

 along the expanded ojjcning unbroken ; and it is not until it has 

 reached the gullet, and the closed mouth prevents any escape of 

 the nutritious matter, that the egg becomes exposed to instru- 

 ments adapted for its perforation. These instruments consist of 

 the hypapophyses of the seven or eight posterior cervical vertebrce, 

 the extremities of which are capped by a layer of hard cement, 

 and penetrate the dorsal parietes of the oesophagus.^ They may 

 be readily seen, even in very small subjects, in the interior of that 

 tube, in which their points are directed backwards. The shell 

 being sawed open longitudinally by these vertebral teeth, the 

 egg is crushed by the contractions of the gullet, and is carried to 

 the stomach, where the shell is no doubt soon dissolved by the 

 acid gastric juice. 



In the Boa and Pythons, fig. 2G6, the teeth are slender, conical, 

 bent backward and inward above their base of attachment. The 

 premaxillary bone in some, ib. 22, is edentulous ; in most it 

 supports four small teeth; each maxillary bone, ib. 21, has a row 



' The Coluher scaler of Linna3us ; an arboreal serpent of South Afriea. 

 ^ Jourdan, in ccxlii. t. vi. p. 100. 



