Stratum (plural, strata)—a single bed or layer of [rock].
Strike—the direction of a real or imaginary line that is formed by the intersection of a bed or [stratum] with a horizontal plane; [strike] is perpendicular to the [dip].
Subconical—less than [conical] in shape; almost a cone.
Suture—the line of junction between two parts; in crinoids, the line of junction between two plates; in gastropods, the line of junction of the whorls as seen on the exterior of the shell; in cephalopods, the line of junction between a [septum] and the shell wall.
Symmetry—orderly arrangement of parts of an object with reference to lines, planes, or points.
[Bilateral] [symmetry]—the symmetrical duplication of parts on each side of a vertical anterior-posterior plane.
[Radial symmetry]—the symmetrical repetition of parts around a common vertical dorso-ventrally disposed axis.
Pentamerous [symmetry]—symmetry arranged in a pattern of fives.
System—the rocks formed during a [period]; the time-stratigraphic term next in rank above a [series].
Taxonomy—that branch of science that deals with classification, especially in relation to plants, animals, or fossils.