Regulus, chosen by lot for the Carthaginian War, marched with his army to a point not far from the Bagrada River and there pitched his camp. In that place a reptile of astonishing size devoured many of the soldiers as they went down to the river to get water. Regulus set out with his army to attack the reptile. Neither the javelins they hurled nor the darts they rained upon its back had any effect. These glided off its horrible scaly fins as if from a slanting testudo of shields and were in some miraculous fashion turned away from its body so that the creature suffered no injury.
Finally, when Regulus saw that it was killing a great number of his soldiers with its bites, was trampling them down by its charge, and driving them mad by its poisonous breath, he ordered ballistae brought up. A stone taken from a wall was hurled by a ballista; this struck the spine of the serpent and caused its entire body to become numb. The formation of the reptile was such that, though it seemed to lack feet, yet it had ribs and scales graded evenly, extending from the top of its throat to the lowest part of its belly and so arranged that the creature rested upon its scales as if on claws and upon its ribs as if on legs.
But it did not move like the worm which has a flexible spine and moves by first stretching its contracted parts in the direction of its tiny body and then drawing together the stretched parts. This reptile made its way by a sinuous movement, extending its sides first right and then left, so that it might keep the line of ribs rigid along the exterior arch of the spine; nature fastened the claws of its scales to its ribs, which extend straight to their highest point; making these moves alternately and quickly, it not only glided over levels, but also mounted inclines, taking as many footsteps, so to speak, as it had ribs.
This is why the stone rendered the creature powerless. If struck by a blow in any part of the body from its bowels to its head, it is crippled and unable to move, because wherever the blow falls, it numbs the spine, which stimulates the feet of the ribs and the motion of the body. Hence this serpent, which had for a long time withstood so many javelins unharmed, moved about disabled from the blow of a single stone and, quickly overcome by spears, was easily destroyed. Its skin was brought to Rome—it is said to have been one hundred and twenty feet in length— and for some time was an object of wonder to all.