Capitate

A valve end, or apex, having the shape of a head, or the shape of a rounded knob.

Other terms for valve ends include subcapitate (less strongly capitate), rostrate, and subrostrate (less strongly rostrate). Subcapitate and subrostrate are quite similar and many taxa may be described as having subcapitate to subrostrate valve ends.

In general, capitate and subcapitate ends are more expanded than the most narrow point on the valve, while rostrate and subrostrate ends are not more expanded than the most narrow point.

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Image Credit: Sarah Spaulding
The headpole of Didymosphenia geminata is distinctly capitate.
Capitate
Image Credit: Marina Potapova
The valve ends of Planothidium haynaldii are broadly capitate.
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Image Credit: Marina Potapova
The ends of Achnanthidium dutheii are capitate.