Ajolote

AKA: Mexican mole lizard

Properly termed bipes biporus, but known as the "five-toed worm lizard" to his friends, this little critter is nicely described at Scrubmuncher's Blog:

Fossorial and seldom seen, precious little is known about the biology of the 160 or so described species of worm lizard. Almost all of them live in the tropics or sub-tropics and it is their admirable adaptations for a subterranean existence that really single them out. Along with their limbs they have all but lost their eyes and they retain just the vestiges of these organs – tiny, beady and covered with a thin scale...

Worm lizards make their tunnels by using their head like a battering ram, a rather brutal, yet effective technique necessitating a heavily reinforced skull where there individual bones of skull are all fused. Some species have a spade-shaped head, which is used to compress the soil into the top of the tunnel, while other species have a keel shaped head they use to press the soil in to the sides of the tunnel by vigorously moving their head from side to side...

In Latin, Amphisbaena means to ‘move in both ways’ reflecting the animal’s ability to move forwards and backwards equally well. Also, in myth and legend the amphisbaena was a fabulous beast with a head at either end of its body, perhaps the brainchild of a medieval chronicler who saw a worm lizard in its defensive posture...

More here, which also has a video showing the ajolote trying to burrow into loose soil.