Septalites

Septalites is a genus of cornulitid tubeworms.

Their shells lack vesicular wall structure and have a smooth lumen filled with numerous transverse septa.

They are externally covered with transverse ridges.

Their fossils are known only from the Silurian of Gotland.

[1]

Septalites septatus longitudinal section of the tube showing septa. Silurian of Gotland