Described is an articulating intervertebral disc prosthesis including a first member having a vertebra engaging portion and a bearing surface; a second member having a vertebra engaging portion and a bearing surface, which in use abuts the first member bearing surface to form a first bearing joint, —and motion restraint means adapted to provide ax-ticulation restraint of the bearing joints at predetermined limits of articulation similar to the natural motion restraint of a facet joint; wherein the prosthesis is longitudinally—split into two bodies so that the two bodies can be laterally separated, each body having an articulating bearing joint. Preferably, the second member bearing surface is shaped to include at least a portion of a first substantially circular curve when viewed in a first section, and at least a portion of a second substantially circular curve when viewed in a second section, said first and second curves being of respectively different sizes of circle. Further described is a chisel and a chisel guide for preparing the disc space for implantation.