DEIRODON. BOA. 221 



devouring their eggs. Now if the teeth had existed of the ordinary 

 form and proportions in the maxillary and palatal regions, the eg^ 

 would have been broken as soon as it was seized, and much of its 

 nutritious contents would have escaped from the lipless mouth of the 

 snake in the act of deglutition ; but, owing to the almost edentulous 

 state of the jaws, the egg glides along the expanded opening 

 unbroken, and it is not until it has reached the gullet, and the 

 closed mouth prevents any escape of the nutritious matter, that the 

 shell is exposed to instruments adapted for its perforation. These 

 instruments consist of the inferior spinous processes 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 young subjects, 

 in the interior of that tube, in which their points are directed back- 

 wards. 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. 



93. Boa. — The simple teeth, ' dentes solidi' as they are termed 

 in Erpetology, are of equal length in a few species of non-venomous 

 serpents ; in the Pythons, Boas and Lycodons they are larger 

 towards the fore-part of the mouth ; but in some Colubers and Tropi- 

 donotes the situation of the larger teeth is reversed. In Dryophis 

 and Psammophis there are a few very long teeth at the middle, and 

 again at the posterior part of the maxillary series. In Xenodon, 

 Coronella and many species of Homalopsis the posterior part of each 

 jaw is provided with a large and simple tooth, which is long and com- 

 pressed in the Xenodon. 



In the Boa Constrictor, the teeth are slender, conical, suddenly 

 bent backwards and inwards above their base of attachment, with the 

 crown straight or very slightly curved, as in the posterior teeth. The 

 intermaxillary bone supports four small teeth ; each superior maxillary 

 bone has eight much larger ones, which gradually decrease in size as 

 they are placed further back : there are eight or nine teeth of similar size 

 and proportions in each premandibular bone. These teeth are sepa- 

 rated by wide intervals, from which other teeth similar to those in 



