DIGESTIVE SYSTEM. 161 



ci'pally upon the edges of the jaws, but occasionally on the palate. 

 In others, the teeth are either uncinate, chisel, awl, or lancet-shaped, 

 finely dentated upon the edges, or deeply serrated at the apices, and 

 occasionally they are conical and blunt. The teeth consist of osse- 

 ous substance, and a coating of enamel, are rarely implanted in dis- 

 tinct sockets, but are either anchylosed externally by their fang to 

 the maxillary bones (denies adnati), while internally the fang is free, 

 and only covered by the gum, or they are firmly (denies innati) an- 

 chylosed to the edges of the jaw. Thus the teeth in Monitor, Basi- 

 liscus, Anolis, Polychrus, Iguana, and others, belong to the first 

 kind, and to the latter those of Calotes, Draco, Stellio, Uromastrix, 

 Chameleon, and Ameira. The teeth are small and blunt in Lacerta, 

 Pseudopus, and Amphisbcena, and denticulated upon the edges in 

 the Monitors. The Crocodiles have pointed, conical teeth, becom- 

 ing blunter posteriorly, and implanted in sockets ; the numerous 

 teeth that are destined to replace them are imbedded, of a conical 

 form, in the interior of the first set. Upon the more minute 

 specific arrangements of the teeth, it is the province of Zoology to 

 dwell. 



The Serpents, when unprovided with poisonous teeth, have 

 curved hook-shaped teeth in the lower jaw, and upon the palatal 

 and supra-maxillary bones, while the small inter-maxillary bone is 

 edentulous, or only rarely toothed, as in Tortrix. In different kinds 

 of Serpents suspected to be dangerous, we meet with a gradual 

 transition from the solid teeth of the non-venomous, to those of the 

 Venomous species. Even in our harmless Snake, the Coluber Natrix> 

 several of the posterior teeth of the upper-jaw appear to be larger 

 and longer than the others. In some other species, formerly in- 

 cluded under the genus Coluber, and in Dipsas, Hornalopsis, &c., 

 the last tooth of the upper jaw is not only longer, but provided with 

 a more or less deep groove, into which the poison escapes from the 

 posterior poison-gland. The superior maxillary bone is shorter in the 

 true Venomous Serpents, and supports upon either side a very long 

 pointed tooth, behind which, several smaller ones are situated with 

 their points curved backward, and which are destined to rise up 

 and replace each other in succession, as they may chance to be lost ; 

 they are all surrounded for the sake of protection with a common 

 wide membranous sheath, formed by an elongation of the substance 

 of the gum. These teeth are either traversed by a demi-groove, 

 open externally, as in Elaps, Naja, Bungarus, or by a closed canal, 

 which stands in communication superiorly with the excretory duct 



11 



