Snakes in the British Museum

Aztec-Mixtec turquoise double-headed snake

 

 Aztec fire serpent

(it's a rattler, see the fangs?)

 Aztec rattlesnake, 

Crotalus durissus

(the Aztecs did like snakes)

 I am not sure what this figure is doing with this snake,

but it's a detail inside a late Egyptian coffin

 This Roman-era Egyptian child's coffin

also has a serpent on the lid.

Also Roman, this detail of "Mithras slaying the bull"

shows a dog and snake drinking the blood of the bull

that the god is spilling.