蚌线; 螺线管; 螺旋线
Conchoid \Con"choid\, n. [Gr. ?; ? shell + ? form: cf. F. concho["i]de.] (Geom.) A curve, of the fourth degree, first made use of by the Greek geometer, Nicomedes, who invented it for the purpose of trisecting an angle and duplicating the cube.