The importance of dentition in distinguishing snakes is seen in the names assigned to them from their teeth alone. In giving a few of these terms we enable the reader to perceive at once, not only how very varied are the systems of dentition, but in what way they vary, the words themselves conveying the description. The names here given are without reference to venomous or non-venomous serpents, but only as belonging to certain families whose teeth present characteristics sufficiently marked to be named by them. From _odous_, _odontos_, a tooth. Anodon, Toothless. Boodon, Ox tooth. Cynodon, Dog’s tooth. Deirodon, Neck tooth. Dinodon, Double tooth. Glyphodon, Grooved or carved tooth. Heterodon, Abnormal tooth. Isodon, Equal toothed. Lycodon, Wolf’s tooth. Ogmodon, Furrowed or grooved tooth. Oligodon, Few toothed. Rachiodon, Spine toothed. Sepedon, Noxious tooth, or a tooth causing putridity. Tomodon, Stump tooth. Xenodon, Strange tooth. In Dumeril’s system very many families, including sometimes several of the above, are grouped according to their teeth, thus:— _Aglyphodontes_, Teeth not carved or notched. _Holodontes_, Whole or entire teeth. _Anholodontes_, Without whole or entire teeth. _Aproterodontes_, Without front teeth. _Isodontiens_, With even teeth. _Apistoglyphes_, Grooved at the back, or the back teeth grooved. _Proteroglyphes_, Grooved in front, or the front teeth grooved. _Solenoglyphes_, Cut or carved with a canal. And some others whose names are equally descriptive. These various characters, with the exception of _Aproterodontes_, which refers to the under jaw, have reference to the upper jaw only. It might be tedious to the reader to enter into a minute description of each of the above groups: sufficient for our present purpose is it to show that such varieties exist, and that a simple, even row of teeth, as a family distinction, is oftener the exception than the rule. Some of the teeth increase in size posteriorly, others are largest anteriorly; others, again, are larger towards the middle of the jaw, and decrease at either end. Some harmless snakes have ‘fangs,’ that is to say, fang-like teeth, but not connected with any poison gland, and at the back instead of the front of the jaw. Again, there are some non-venomous species that have the power of moving these fang-like teeth, raising or depressing them as vipers move their fangs, and as will be further described presently. Some grooved teeth convey an acrid saliva, others are without any modification of saliva, the long teeth being of use in holding thick-skinned prey.