TERMINOLOGY5. Rims
TERMINOLOGY| Shield | broad (sub-)horizontal structure (placoliths). |
| Tube | (sub-vertical structure between two shields (placoliths). |
| Wall | (sub-)vertical structure not associated with shields (muroliths). |
| Flange | (sub-)horizontal protrusion from rim. |
| Collar | (sub-)vertical protrusion from rim (may occur on proximal or distal surface). |
| Crown | discontinuous/beaded collar. |
| Radial | direction in the surface of the baseplate perpendicular to its margin: Inward-outward - toward-away from centre. | |
| Tangential | direction in the surface of the baseplate parallel to its margin: Clockwise/dextral/right, anticlockwise/sinistral/left senses of direction as seen in distal view. We recommend: use of clockwise/anticlockwise as the clearest of these terms for general purposes. Use of dextral/sinistral when it is wished to particularly emphasise that this is the orientation as seen in distal view. | |
| Vertical | direction perpendicular to the baseplate: Up/down distal-proximal directions. | |
| Flare and taper | divergence of orientation from horizontal/vertical in the radial direction. Flare surfaces diverge upward, producing obconical/funnel-shaped bodies. Taper surfaces converge upward, producing conical bodies. |
| Imbrication/inclination | divergence from horizontal in the tangential direction. Imbrication is applicable to a cycle of elements, inclination to individual elements. |
| Clockwise/anticlockwise imbrication | offset of upper part of element from lower. |
| Imbrication angle | angle of contact-surface from the horizontal. High-angle - sub-vertical contact-surfaces. Low-angle - sub-horizontal contact-surfaces. |
| Zeugoid rim | rim with high-angle imbrication, and without distinct shields. (Alternative terms loxolith rim, zygodiscid rim, see appendix). |
| Obliquity | horizontal divergence from radial direction. (Alternative term precession, see appendix). |
| Dextral/sinistral obliquity | deflection from radial of outer part of element relative to inner part, as seen in distal view. Note that elements will show opposite apparent senses of obliquity in distal and proximal view. This can be described as follows: a dextrally oblique cycle displays clockwise obliquity in distal view but anti-clockwise obliquity in proximal view. |
| Butting | elements with simple (sub-)radial sutures. |
| Interlocking | elements with complex sutures. |
| Overlapping | elements with low angle oblique sutures (N.B. This pattern has occasionally been described as imbrication, but we prefer to use imbrication for description of vertical structures). |
