Apex

noun

(L. apex: tip, summit) (pl. apexes or apices) The tip or summit of an organ; the uppermost point; the narrowed or pointed end; the point farthest from the point of attachment. Part of gastropod shell that was formed first; typically pointed, at the posterior end of the shell, consisting of the protoconch or smallest whorls of the spire. Apical = having to do with the apex.