Longitudinal canal

A chamber having the shape of a tube inside the valve, oriented along the apical axis. It occurs in genera such as Neidium and Muelleria, which have valves consisting of two layers of silica with the canal lying between them. The canals appear as longitudinal lines and may be central or marginal.

Longitudinal Canal
Image Credit: Sarah Spaulding
The genus Neidium possesses longitudinal canals that are positioned at the valve margin.