Which animal's Latin (scientific) name means ‘tooth-walking seahorse’ in English?

I heard a story, meaning I don't vouch for its veracity, that Walrus are about the only animal that a polar bear won't attack. The big tusks can do real damage to bear. So polar bears are weary of thumping on the ground, as Walrus do. If you face a polar bear and jump up and down the thumping sound/vibration will deter it. I have not tried this and have no intention of doing so.