_Tropidonotus._ Posterior maxillary teeth longest; mandibular teeth not more than 20, posterior smallest _Zamenis._ Maxillary teeth subequal; mandibular teeth 20 to 25, posterior smallest _Coluber._ _b._ Mandibular teeth 14 or 15, subequal; maxillary teeth 12 to 15. Maxillary teeth increasing in size _Coronella._ Maxillary teeth subequal _Contia._ _B._ One or two enlarged grooved fangs behind the series of solid maxillary teeth. 14 to 17 subequal solid maxillary teeth, forming a continuous series; 21 to 23 mandibular teeth, anterior strongly enlarged _Coelopeltis._ 9 to 11 solid maxillary teeth, fourth and fifth or fifth and sixth enlarged, followed by an interspace; sixth mandibular tooth fang-like, followed by an interspace _Macroprotodon._ 9 or 10 solid maxillary teeth, forming a continuous series, decreasing in length posteriorly; anterior mandibular teeth strongly enlarged _Tarbophis._ _C._ Maxillary with only two large canaliculated fangs side by side, one of which may be missing; anterior mandibular teeth longest _Vipera_, _Ancistrodon_. [Illustration: FIG. 12--MAXILLARY AND MANDIBLE OF--(_a_) _Tarbophis fallax_; (_b_) _Coelopeltis monspessulana_; (_c_) _Macroprotodon cucullatus_. (From British Museum Catalogue of Snakes)] In counting the teeth for the purpose of using this key, care must be taken to ascertain the full number, as it frequently happens that one or more are missing; but their place is indicated by the shallow pits in which their base was implanted, the overlooking of which might convey the impression of a hiatus such as is characteristic of certain genera--_Macroprotodon_, for instance. Needless to say, the loose teeth which are in reserve on the inner side of the jaws or behind the tubular fangs are not taken into consideration, the numbers given being those of functional teeth only. Although as a rule the teeth can be counted easily, on a specimen preserved in spirit, by simply pushing aside the lips and gums with the finger, it is sometimes necessary to remove and clean the bones of the jaws, an operation which does not require much skill. ------------------------------------------------------------------------ CHAPTER VI POISON APPARATUS--DIFFERENT KINDS OF POISONS