Glossary
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Axial costa
An axial costa is an internal, narrow ridge of silica positioned along the axial area.
Mastogloia smithii is a taxon with two internal axial costae. Together, the axial costae form the sides of a groove, or gutter (Paddock and Kemp 1990). The axial costae widen slightly at the central nodule and terminate near the distal raphe.
See also costa.
Alternative Terms
- longitudinal rib
A longitudinal rib is similar to an axial costa, but in general, a longitudinal rib is more rounded and relatively wider. Longitudinal ribs are found in the genus Amphipleura and Frustulia.
Citations
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Publication Link: doi:10.1080/0269249X.2014.889038
Image Credit: B. Van de Vijver
Image Credit: B. Van de Vijver
Image Credit: B. Van de Vijver
Scanning electron micrograph of the inside of a valve of Mastogloia smithii. Arrows indicate the axial costae on either side of the raphe.
Image Credit: B. Van de Vijver
Light micrographs of Mastogloia smithii, at two different focal depths. Each arrow indicates an axial costa.