Dyspholidus typus - The Boomslang
Though it belongs to the same family as king snakes and the most common “grass snakes”, the boomslang is one of the few members of Colubridae to possess a venom that’s legitimately dangerous to humans, and the fangs that are able to inject it (some members of the family have venom, but weak fangs). In fact, the fangs of the boomslang are some of the broadest and most deeply-grooved in the snake world.
The venom of the boomslang is hemotoxic. That means that the proteins in the venom affect the blood of the victim, and in the case of the most common hemotoxin in boomslang venom (phospholipase A2, if you’re wondering), it causes red blood cells to rupture. Given enough time with this toxin floating around in the bloodstream, the significant thinning of the blood allows it to flow out of the capillary walls, and can flow out of any part of the body where capillaries are particularly close to the exposed surface.
In other words, if you’re bitten by a boomslang and don’t seek help right after being bitten, you’ll likely end up bleeding out from your nose, eyes, mouth, ears, and genital orifices. Because of the significant blood loss associated with a wait of more than 48 hours between bite and antivenin administration (phospholipases are fairly slow-working, compared to neurotoxins and cardiotoxins), full blood transfusions are sometimes needed, to replenish the plasma, red blood cells, and platelets that were lost in the bleed-out.
Illustrations of the Zoology of South Africa. Andrew Smith, 1888.