In Dr. Günther's _first sub-order_, that of _Non-Venemous Snakes_, the teeth are either entirely smooth, or only the last of the maxillary series is provided with a faint longitudinal groove, which is not intended to convey a virus into the wound, the groove appearing rather to increase the strength of the tooth. Many of them have long teeth in front of the jaws or of the palate, but these are never grooved or perforated, and only serve to afford a firmer hold on the living and struggling prey. "The structure of the venom-tooth is not the same in all poisonous Snakes: in some it is fixed to the maxillary bone, which is as long or nearly as long as in the non-Venemous Snakes, and generally bears one or more ordinary teeth on its hinder portion. The venom-tooth is fixed more or less erect, not very long, and its channel is generally visible as an external groove. The poisonous Snakes with such a dentition have externally a more or less striking resemblance to the non-Venemous Serpents, and on this account they are designated as _Venemous Colubrine Snakes_, forming our _second sub-order_." Two very distinct families are here brought together--viz. the _Elapidæ_ (which comprises the Cobras and many others), and the _Hydrophidæ_ (or Sea Snakes). "In the other Venemous Snakes, composing the _third sub-order_, the maxillary bone is extremely short, and does not bear any teeth except an exceedingly long fang, with a perfectly closed externally invisible channel in its interior. Although this tooth also is fixed to the bone, the bone itself is very mobile, so that the tooth, which is laid backwards when at rest, can be erected the moment the animal prepares to strike. This tooth or fang, like all the other teeth, is not only occasionally lost, but appears to be shed at regular intervals. From two to four other venom-fangs in different stages of development, destined to replace the one in action, exist between the folds of the gum, and are not anchylosed to the bone." The more characteristic Venemous Snakes appertain to this sub-order--viz. the two families _Crotalidæ_ (comprehending the Rattlesnakes, the Fer-de-lance, &c.) and _Viperidæ_ (comprising the Vipers, Puff-adders, &c.). Let it be particularly borne in mind that the supposed distinguishing characters of all poisonous Snakes, as assigned by sundry mischievously ignorant writers, are those of the third of the foregoing sub-orders almost exclusively. Even the broad, flat, and lanceolate form of head is exemplified in certain Tree Snakes of the non-Venemous genus _Dipsas_, and not in the Cobras and others that are quite as deadly--e.g. _Hoplocephalus_, _Bungarus_, _Naja_, _Elaps_, and others constituting the Colubriform family _Elapidæ_. FIRST SUB-ORDER. _Ophidii Coluberiformes_ (Günther), Innocuous Snakes. These are distributed by Dr. Günther under numerous families, of which we can only notice the more prominent, and some of the more conspicuous species, in a popular exposition.