顶石
Capstone \Cap"stone`\, n. (Paleon.)
A fossil echinus of the genus {Cannulus}; -- so called from
its supposed resemblance to a cap.
capstone
n 1: a final touch; a crowning achievement; a culmination [syn: {finishing
touch}, {copestone}]
2: a stone that forms the top of wall or building [syn: {copestone},
{coping stone}, {stretcher}]