Illustrations of Shell Features
Even though one of the definitions of a suture is "a furrow at the junction of adjacent bodily parts," strictly speaking the suture on a univalve (when present) is the line where whorls attach to each other. This line may be visible or obscured by the shape of, or sculpture on the "subsequent" whorl. The suture itself is a one-dimensional line on the surface of the "prior" whorl. A suture should not be labelled “deep” or “shallow.” However, it is often the case that authors describe sutures this way. When this is done, what is most often being described is the distance between the line of the suture and the virtual conoid plane connecting the peripheries of the teleoconch whorls or another distinctive, proximate feature, such as a collar-like structure. A shell with whorl peripheries more distant from the axis is often described as having a "deeper” suture than one with peripheries less distant from the axis. All this may be rather subjective and vary in the context of different genera. What is often describe as characters of the suture are really about the shape of whorls, the sculpture adjacent to it, or where it falls on or in the sculpture of the prior whorl. For example, if the sutural line runs along the bottom of a deep groove preexisting on the prior whorl, it may be described as deep when it should be described as running along the bottom of a deep groove on the prior whorl. Descriptions of sutures should be limited to location on the prior whorl, form of the line, and visibility with indication of pertinent adjacent sculptural features (e.g., obscured by a collar, raised ridge or covered by subsequent shell growth).