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"Tribulus, a caltrop, also called murex. When a place was beset with troops, the one party endeavoured to impede the cavalry of the other party, either by throwing before them caltrops, which necessarily lay with one of their four sharp points turned upward, or by burying the caltrop with one point at the surface of the ground. The following wood-cut is taken from a bronze caltrop figured by Cayius." &mdash Smith; 1873

Tribulus

"Tribulus, a caltrop, also called murex. When a place was beset with troops, the one party endeavoured…