To search for terms starting with a certain letter, click a letter in the bar below.
The glossary provided here is largely based on “Seashells of Southern Florida: Bivalves,” by Paula M. Mikkelsen & Rüdiger Bieler, Princeton University Press. Production of this glossary was funded in part by the National Science Foundation’s Partnerships in Enhancing Expertise in Taxonomy [PEET] Program, NSF-DEB-9978119, “Bivalves - Research, Training, Electronic Dissemination of Data” (1999-2008) to Bieler and Mikkelsen.
- UMBO (pl. UMBOS or UMBONES)
Rounded or pointed extremity of a bivalve shell, often projecting above the HINGE line, that reflects the early growth stage (= oldest part of the shell) and includes the PRODISSOCONCH and adjacent convex area; also called beak (some authors treat beak and umbo as synonymous, but with some Bivalvia the umbos are above the beak) (figure: Dosinia discus).
- UMBONAL CAVITY
- Space inside the valve within the UMBO and under the HINGE PLATE.
- UMBONAL CRACK
- Crack in the shell of Periplomatidae that occurs naturally at the umbone of each valve (figure: Periploma margaritaceum).
- UMBONAL REFLECTION
Anterodorsal valve margin that is turned up and over the UMBO; also called flange or shield; occurring in such families as Pholadidae and Teredinidae (figure: Pholas campechiensis).
- UMBONAL RIDGE
- Prominent angled or rounded feature on the external shell surface that begins at the UMBO and runs obliquely posteriorly to the ventral border.
- Smoothly wavy, usually referring to a shell or MANTLE margin.