For the Brazilian specimens, I am indebted to Dr. Arthur Stradling, who presented me with the snakes, out of whose jaws I myself procured them. In this _Lachesis_ there were two fangs _visible_ on one side, and only one on the other, viz. the functional pair, and one nearly ready to replace one of these. In addition to the pair were four reserve fangs hidden under the functional one on the right side. I say ‘under,’ because anatomically they were _beneath_, though locally _above_ when the snake was in its natural position. All these five fangs I got from only one side, and in addition some others too small to represent. There may be yet more in the membranous capsule, as mine was a sadly unscientific search for them, and without any very powerful magnifier. Like Charas, I ‘grovelled’ for them! From a young _Jararaca_ I also got out the functional and four or five supplementary fangs from one side, also an exceedingly small and short jaw-bone, leaving the other side undisturbed. Even the principal fang (_d_) is too fine to represent faithfully in printer’s ink; the others are to the naked eye and to the touch almost impalpable. When we reflect on the exquisite sharpness and finish of these minute weapons, and the fatal injury they are capable of inflicting, we are filled with awe and amazement at the virulence of the subtle fluid which oozes through that almost invisible aperture. The brother of this tiny African viper (_f_), when only a few hours old, struck a mouse, which was dead in less than one minute. The whole forty-six of them (p. 321) were born with the ‘murderous teeth’ in their vicious little jaws. The fang here represented was loose in its mouth. A pair of perfect functional fangs remained. [Illustration: Fangs and some simple teeth from my specimens. _a._ Functional fang and four supplementary fangs from _Lachesis mutus_ (Brazil). _b._ Rattlesnake fang. _c._ Fang of young rattlesnake (Brazil). _d._ Fang of young _Jararaca_ (Brazil). _e._ Pseudo ‘fang’ of _Xenodon_ (Brazil). _f._ Loose fang from the mouth of _Vipera nasicornis_, aged one week. _g._ Portion of palate bone bearing four teeth, from _Lachesis mutus_ (Brazil). _h._ Two lower teeth from the same.] Picture to yourselves the intensity of that invisible molecule of venom, which could ooze through an equally invisible aperture in this last diminutive weapon, and be fatal to life in a minute of time! From the effects observed on victims, I am inclined to place these large African vipers amongst the most venomous of all serpents of their size.